Jaundice, which is observed in almost every newborn, is termed “physiologic” because it clears within a few days, after activation of bilirubin conjugation. This phenomenon reflects a unique feature of prenatal life: Many functions of the liver that are required after birth for nutrition, metabolic balance, and detoxification and excretion of endogenous chemicals are provided to the developing fetus by the placenta and the mother. “Pathologic” jaundice is the most frequent indication for liver biopsy in children, especially infants, because functional immaturity is not limited to glucuronidation, and intrinsic defects in many processes and structures lead to cholestasis. This is even more evident in premature infants. Not only do the first challenges to hepatobiliary function account for liver diseases that “adult” pathologists encounter very rarely, but maternal-fetal interactions are not always beneficial. Certain infections and immunologically mediated injuries are observed only in infants.
This chapter focuses on constitutional deficiencies of the liver that necessitate examination of tissue for diagnosis and treatment. Myriad chromosomal imbalances and heritable mutations that manifest with dysmorphism and multisystem disease, such as Down syndrome, may affect the liver but can be diagnosed clinically; they are included in this chapter only if they offer a challenge to diagnosis. Anatomic and synthetic defects, such as clotting factor deficiencies that do not lead to hepatobiliary dysfunction, are covered in other publications.
We have incorporated a practical approach to liver biopsy that is derived from Jevon and Dimmick’s classification of the histologic pattern of pediatric liver biopsies, which identify six dominant patterns. Finally, the progress made during the past decade with regard to decoding the genetic basis of disease has resulted in improved therapeutics as well as reclassification and renaming of disease entities, genes, and proteins. In the preparation of this chapter, we have benefited from Online Mendelian Inheritance in Man (OMIM; www.omim.org ), an online compendium of human genes and phenotypes maintained by the Johns Hopkins University and developed by the National Center for Biotechnology Information (NCBI). This searchable database provides a unique accession number for each entity and incorporates all alternative disease names and gene nomenclature. Throughout the text and in the tables, we have provided OMIM numbers for heritable conditions that may be beneficial to readers.
Pediatric Liver Biopsies
Indications for Liver Biopsy in Children
Other than prior liver or bone marrow transplantation (see Chapter 42 ), the most common indications for liver biopsy in the pediatric age group are conjugated hyperbilirubinemia in young infants ( Table 54.1 ); tumor diagnosis (see Chapter 55 ); and assessment of liver injury, inflammation, and fibrosis. Metabolic diseases may manifest with fetal demise immediately after birth or at any age thereafter ( Table 54.2 ).
|Age||Hepatic Failure Encephalopathy (±Bleeding)||Jaundice (Hepatitis)||Failure to Thrive and/or Hepatomegaly||Portal Hypertension (Ascites, Bleeding, Splenomegaly)|
|Newborn||Galactosemia, mitochondriopathies, urea cycle defects, glutaric aciduria II||Crigler-Najjar syndrome type I||Leprechaunism, fructose 1.6 diphosphatase deficiency|
|First 2 mo||Wolman disease, tyrosinemia, perinatal hemochromatosis||α 1 -Antitrypsin deficiency, NPD type C||GSD 1a, Ib||Zellweger syndrome||GSD IV|
|First 6 mo||Hereditary fructose intolerance, LCAD deficiency, carnitine deficiency, propionic acidemia||Byler disease, Alagille syndrome, THCA, 3β-HSD, isomerase deficiency||GSD III||Lysinuric protein intolerance, MPS, other storage diseases|
|First 2 yr||MCAD deficiency, mitochondriopathies||Cystic fibrosis, Rotor syndrome||GSD VI and IX, congenital disorder of glycosylation type Ib, glycoprotein|
|Up to 6 yr||Reye syndrome||Cholesterol ester storage, NPD types A and B, cystinosis, hereditary fructose intolerance|
|Puberty/and adolescence||Wilson disease, erythropoietic porphyria||Gilbert syndrome, Wilson disease, Dubin-Johnson syndrome||α 1 -Antitrypsin deficiency, Wilson disease, lipoatrophic diabetes|
|Adults||Gaucher disease, citrullinemia, hemochromatosis|
For young infants with conjugated hyperbilirubinemia, extrahepatic biliary atresia (EHBA) is the one condition that is amenable to surgical treatment. Choledochal cysts and other rare causes of duct obstruction that lead to jaundice shortly after birth are rare and are typically diagnosed by imaging studies rather than liver biopsy. Biliary atresia must be recognized quickly if surgical hepatic portoenterostomy is to be successful in reestablishing biliary drainage. Biopsy specimens from these patients are often obtained before the results of noninvasive studies, such as protease inhibitor typing, are available. Even in infants with probable biliary atresia, a liver biopsy may be performed to exclude other potential causes of jaundice. Therefore, clinical management decisions rely heavily on morphologic assessment of liver biopsy specimens ( Table 54.3 ). After exclusion of biliary atresia and infections, consideration should be given to the possibility of an inherited disease as the cause of the patient’s illness.
|Find treatable condition||Obstruction|
|Prevent inappropriate treatment||α 1 -Antitrypsin deficiency mimics EHBA|
|No surgery for Alagille syndrome|
|Secure samples for diagnosis||Urine for FAB-GC/MS for bile acids|
|Frozen liver for enzymes|
|PCR for virus|
|Provide data for family||Hereditable conditions|
|Monitor course of treatment and prognosis||After Kasai procedure or transplantation, biopsies and serial α-fetoprotein levels|
|Elucidate pathogenesis (with a goal of prevention)||Role of fasting versus TPN|
In older children, hepatomegaly, liver tumors, or chronic liver disease may prompt a liver biopsy. When liver disease appears after the neonatal period, clinical studies are typically used to identify the specific cause of the disease. Clinically diagnosed disorders include hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, Wilson disease, reticuloendothelial storage disorders, steatosis, drug-induced hepatitis, autoimmune hepatitis, and cholangiopathy. Unusual causes include Alagille syndrome and metabolic storage disorders. On occasion, liver tissue may be obtained from a child with portal hypertension in whom none of these conditions is suspected. In such cases, congenital vascular anomalies (see Chapter 51 ) and congenital hepatic fibrosis should be considered. Liver biopsies are used to assess the severity of disease and the response to treatment in all of these disorders.
Pediatric Liver Biopsy Specimen
Because of the broad range of diseases in children, evaluation of liver biopsies in these patients is distinct from that in adults. To perform all potentially necessary tests on a liver biopsy specimen, prior arrangements should be in place to ensure adequate specimen processing ( Table 54.4 ).
|Snap-freezing||Use liquid nitrogen; core tissue 2 cm in length; air-sealed specimen vial|
|Electron microscopy||Use electron microscopy fixative; core tissue 0.3 cm in length|
|Formalin fixation||Use neutral-buffered formalin; core tissue 1 cm in length|
Formalin-fixed specimens should be processed for routine light microscopy. Serial sections should be obtained. For example, a ribbon of 20 sections may be placed on 10 slides, with two tissue sections per slide. The first and last slides should be stained with hematoxylin and eosin (H&E). Periodic acid–Schiff (PAS) stain with and without diastase digestion, trichrome stain, Perls iron stain, and reticulin techniques may be used on intervening slides. The remaining slides may be held for possible future use.
Normal and Potentially Misleading Features of the Liver in Infants and Children
Some key features in the liver of infants and children differ from those in adult liver ( Table 54.5 ). Variations occur in architecture, specific cell populations, content of hepatocytes, and response to injury.
|Architecture||Physiologic hyperplasia: liver cell plates two cells thick|
|Residual ductal place architecture, particularly at periphery of liver|
|Extramedullary hematopoiesis||Portal tracts: granulocytic extramedullary hematopoiesis|
|Parenchyma: erythropoietic extramedullary hematopoiesis|
|Hepatocyte contents||Hemosiderin granules |
The liver undergoes substantial growth after birth. It normally doubles in weight within the first month of life, doubles again during the first year of life, and does not reach its mature size until late adolescence. The portal tract system grows in parallel with the liver. Therefore, the most peripheral aspects of the liver may exhibit developmental residua of fetal histology. For instance, residual bile duct plates may rim the portal tracts, and the latter contain a more cellular mesenchyme and a centrally placed portal vein ( Fig. 54.1 ). The dimensions of hepatic lobules remain constant with growth. However, hepatocyte cords may remain two cells thick well into the fourth postnatal year. This should not be misinterpreted as regenerative hyperplasia in response to tissue injury.
Hematopoietic elements are commonly present in liver biopsy specimens obtained during the postnatal months. Granulopoiesis predominates in portal tracts, whereas erythropoiesis is common in the parenchyma.
Until a postnatal age of approximately 3 months, hepatocytes normally contain copper-binding protein and copper (demonstrable by orcein and rhodanine techniques, respectively) and granules of hemosiderin, particularly in periportal hepatocytes. These deposits are considered to be physiologic and disperse with time. Conversely, hepatocyte alterations characteristic of various storage disorders may be inconspicuous in early infancy because of the time required to accumulate abnormal substances, such as α 1 -antitrypsin (A1AT). One dramatic exception to the concept of physiologic iron deposition occurs in newborns who exhibit liver failure at birth, which is usually attributable to severe liver injury in utero. In this scenario, marked iron deposits may be present in hepatocytes at birth, giving rise to the term neonatal iron storage disease, or perinatal hemochromatosis . A severe degree of necrosis and fibrosis is also present in patients with this condition. The extrahepatic reticuloendothelial system does not exhibit iron accumulation, a fact that highlights the primacy of the liver injury. The finding of severe perinatal hepatic siderosis is nonspecific and indicates the development of liver injury during gestation. A lesser degree of hemosiderosis, with reticuloendothelial system deposits, may be seen in cases of maternal-fetal blood group incompatibility with significant hemolysis.
Response to Injury
Giant, multinucleated hepatocytes, with or without bile pigment, are commonly present in infants with liver disease, regardless of the etiology. This change is considered nonspecific and reactive. Multinucleated hepatocytes are formed by syncytial breakdown of cell–cell borders but with partial preservation of the canalicular aspects of the cell membrane. The canalicular remnants, with retained bile, may be observed within the cytoplasm. Giant cells exhibit multiple nuclei, either scattered throughout the cytoplasm or clustered toward one pole of the cell. This reaction may persist well into childhood if the inciting disorder is not resolved. Multinucleated giant cell change is unusual in older children and adults, but it may occur in some disorders, such as autoimmune hepatitis and paramyxovirus hepatitis.
The histologic spectrum of neonatal hepatitis includes giant cell change in hepatocytes, intralobular cholestasis, necrosis of hepatocytes, and intrahepatic hematopoiesis. All of these features are nonspecific events in infancy and can be observed in EHBA, A1AT storage disorder, and many other conditions ( Table 54.6 ). With advances in biochemistry and molecular genetics, many conditions formerly grouped within the category of neonatal giant cell hepatitis can now be specifically diagnosed, including progressive familial cholestasis types 2 and 3 and various bile salt synthetic defects.
|Normal or Low GGT||Elevated GGT|
|Infantile Cholestasis without Giant Cells (±Bile Duct Damage)|
|Infantile Cholestasis Plus Necrosis (±Steatosis)|
Approach to the Diagnosis of Pediatric Liver Disorders in Liver Biopsies
When evaluating pediatric liver biopsy specimens, a careful review of patient age at disease onset (see Table 54.2 ), clinical manifestations, and routine laboratory workup findings is essential ( Table 54.7 ). If the presentation includes hepatomegaly, awareness of extrahepatic involvement is also helpful ( Table 54.8 ). It is useful to initially classify the histologic pattern of disease into one of the six patterns of injury described initially by Jevon and Dimmick. Although these patterns often overlap, it is usually possible to define the predominant pattern in an individual case. This section describes an algorithmic approach to the diagnosis of liver disorders, beginning with the histologic patterns of tissue injury (see Boxes 54.1 through 54.6 ). A detailed description of the major entities is found later in the chapter.
|Soon After Birth||Short Delay||Insidious Onset|
|Steatohepatitis (liver biopsy)||Biliary cirrhosis (liver biopsy)||Sly (fibroblast culture; β-galactosidase)||GSD type IV (liver; branching enzyme)|
|Budd-Chiari (MRI)||NPD type C (fibroblast culture; cholesterol esterification)||Wolman (fibroblast culture; acid lipase)||GSD type VIII (liver; phosphorylase B)|
|GSD type VI (liver; phosphorylase)||Cholesteryl-ester storage disease (fibroblast culture; acid lipase)||NPD type C (fibroblast culture; cholesterol esterification)||Sialidosis (fibroblast culture; neuraminidase)|
|GSD type IX (liver; phosphorylase kinase)||NPD type B (leukocyte; acid sphingomyelinase)||Mannosidosis (fibroblast culture; α-mannosidase)|
|GSD type X (liver; complement C3 and C5, AMP-dependent kinase)||Fucosidosis (fibroblast culture; α-fucosidase)|
|Congenital disorder of glycosylation type Ib (serum transferrin)||NPD type A (leukocyte; acid sphingomyelinase)|
Giant cell hepatitis
Consider progressive familial intrahepatic cholestasis type 2 (PFIC2) → EM: amorphous canalicular bile → confirm with ABCB11 gene sequencing
Dilated canaliculi with pale bile
Centrilobular fibrosis → progressive familial intrahepatic cholestasis type 1 (PFIC1) → EM: coarse granular canalicular bile → ATP8B1 gene sequencing (30-40% positive)
No fibrosis → benign recurrent intrahepatic cholestasis → confirm with ATP8B1 or ABCB11 gene sequencing
EM: dense amorphous canalicular bile
PFIC2 → as above
arthrogryposis, renal dysfunction, and cholestasis (ARC) syndrome → in the setting of arthrogryposis, perform VPS33B and VIPAR gene sequencing
familial hypercholanemia (FHCA) → TJP2 and BAAT and EPHX1 gene sequencing
Bile duct/portal tract ratio > 0.9
Giant cell change ± cirrhosis → consider progressive familial intrahepatic cholestasis type 3 (PFIC3) → confirm with ABCB4 gene sequencing
Cirrhosis with prominent bile ductular proliferation → North American Indian childhood cirrhosis (NAIC) → confirm with CIRH1A gene sequencing
Hepatocellular siderosis → confirm with iron stain → GRACILE syndrome → confirm with BCS1L gene sequencing
Giant cell hepatitis ± cirrhosis → PAS-positive diastase-resistant hepatocyte inclusions → A1AT staining by immunohistochemistry → α 1 – Antitrypsin ( A1AT) deficiency → EM: homogeneous inclusions within RER → confirm with Pi typing
Giant cell hepatitis ± cirrhosis → PAS negative → consider Niemann-Pick disease type C → EM: membrane-bound laminated structures and dense osmiophilic bodies → confirm with filipin staining in cultured fibroblasts and cholesterol esterification assays, or NPC1 and NPC2 gene sequencing
Neonatal sclerosing cholangitis with ichthyosis due to claudin-1 ( CLDN1 ) mutation
Bile duct/portal tract ratio < 0.9 (ductopenia)
Giant cell hepatitis and cirrhosis → consider Alagille syndrome (AGS) → confirm with JAG1 (and NOTCH2 ) gene sequencing
Giant cell hepatitis with bridging fibrosis or cirrhosis → PAS-positive diastase-resistant hepatocyte inclusions → A1AT staining by immunohistochemistry → A1AT deficiency → as above
EM , Electron microscopy; GGT , γ-glutamyltransferase; GRACILE , g rowth r etardation, a mino aciduria, c holestasis, i ron overload, l actic acidosis, and e arly death; PAS , periodic acid–Schiff; RER , rough endoplasmic reticulum.
Consider mitochondrial electron transport chain (ETC) disorders → confirm with specialized testing (enzymatic activity of ETC complexes; mtDNA analyses)
Oncocytic transformation → Consider mtDNA depletion syndrome (MDS) → EM: enlarged pleomorphic mitochondria with unusual cristae → confirm with specialized testing including genotyping dGUOK , POLG , etc.
EM: enlarged mitochondria with increased cristae → consider fatty acid oxidation (FAO) disorders → hypoketotic hypoglycemia → confirm with specialized testing including gene sequencing for ACADM , ACADL , etc. (see Table 54.10 )
Hepatocyte vacuolation, foamy Kupffer cells, macrophages with positive lipid stains → consider Wolman disease → see Box 54.3
Hepatocyte stainable copper → consider Wilson disease → see Box 54.4
Inspissated material within bile ducts → consider cystic fibrosis (CF) → confirm with CFTR gene sequencing, sweat chloride testing
Cholestasis without cirrhosis
Consider hereditary fructose intolerance (HFI) → confirm with fructose-1-phosphate aldolase assay on liver tissue and ALDOB sequencing
Hepatocyte cytoplasmic storage
Consider glycogen storage disease (GSD) types I, III (see Box 54.3 ), VI, and IX
EM , Electron microscopy; mtDNA , mitochondrial DNA.
Membrane-Bound (Lysosomal) Inclusions by Em
Hepatocyte microvesicular steatosis
Lipid stains positive → Wolman Disease/cholesterol ester storage disease (CESD) → EM: cholesterol crystals → confirm with enzyme activity and LIPA gene sequencing
Predominantly RES involvement with hepatocyte sparing
Histiocytes, Kupffer cells with “crinkled-paper” inclusions → Gaucher disease → EM: tubular structures → confirm with enzyme activity and GBA gene sequencing
Foamy histiocytes and lipogranulomas → Farber disease → EM: curvilinear structures → confirm with enzyme activity and ASAH1 gene sequencing
Foamy histiocytes and hepatocytes
PAS negative → Lipid stains positive → Niemann-Pick disease type A → EM: myelin-like figures → confirm with enzyme activity and SMPD1 gene sequencing
PAS positive → EM: monoparticulate glycogen ( Pompe disease [GSD type II] ); fibrillogranular material or empty vacuoles ( mucopolysaccharidoses or GM1 gangliosidosis ) → confirm with enzyme activity and gene sequencing
Wolman disease or Gaucher disease → as above
Exclusively Cytoplasmic Storage by Em
PAS positive, diastase sensitive → von Gierke disease (GSD type I) → confirm with enzyme activity on fresh liver tissue
PAS positive, diastase resistant → colloidal iron positive → EM: amylopectin-like fibrillary structures → Andersen disease (GSD type IV) → confirm with enzyme activity and GBE1 gene sequencing
PAS positive, diastase sensitive → GSD type III → confirm with enzyme activity
EM , Electron microscopy; GSD , glycogen storage disease; PAS , periodic acid–Schiff; RES , reticuloendothelial system.
Giant cell hepatitis
PAS-positive diastase-resistant hepatocyte inclusions → A1AT staining by immunohistochemistry → consider α 1 -Antitrypsin ( A1AT) deficiency → see Box 54.1
Consider mitochondrial hepatopathies → see Box 54.2
Increased hepatocyte stainable copper
Consider Wilson disease → EM: pleomorphic dilated mitochondria → confirm with hepatic copper content >250 µg/g dry weight; urinary copper excretion after penicillamine challenge >25 µmol/24 hr → DNA haplotype analysis and/or ATP7B gene sequencing in affected families
EM , Electron microscopy; PAS , periodic acid–Schiff.
Hepatocyte vacuolation and foamy Kupffer cells, macrophages
Lipid stains positive → consider Wolman disease → EM: cholesterol crystals → confirm with enzyme activity and LIPA gene sequencing
Increased hepatocyte stainable copper
Consider Wilson disease → see Box 54.4
Increased hepatocyte iron
Consider hereditary hemochromatosis (HH) → measure hepatic iron (hepatic iron index > 2) → confirm with HFE testing
Giant cell hepatitis
PAS-negative → consider tyrosinemia → confirm with elevated blood/urine succinylacetone levels
Cholestasis, steatosis → consider mitochondrial hepatopathies → see Box 54.2
Hepatocyte And/or Res Inclusions
Exclusively cytoplasmic inclusions on EM
PAS positive, diastase sensitive → GSD type III → see Box 54.3
Membrane-bound (lysosomal) inclusions on EM
Histiocytes, Kupffer cells with “crinkled-paper” inclusions → Gaucher disease → see Box 54.3
PAS-positive inclusions → EM: fibrillogranular material or empty vacuoles ( mucopolysaccharidoses ) → see Box 54.3
Normal GGT cholestasis
Consider progressive familial intrahepatic cholestasis type 2 (PFIC2 ) or PFIC1 → see Box 54.1
High GGT cholestasis
Consider PFIC3 , North American Indian childhood cirrhosis (NAIC) , Alagille syndrome → see Box 54.1
Giant cell hepatitis → PAS negative → consider Niemann-Pick disease type C → see Box 54.1
EM , Electron microscopy; GGT , γ-glutamyltransferase; PAS , periodic acid–Schiff; RES , reticuloendothelial system.
Consider glycogen storage disease (GSD) type I → see Box 54.3
Storage pattern → consider GSD type I → see Box 54.3
Consider α 1 -Antitrypsin (A1AT) deficiency → see Box 54.1
Increased hepatic iron → consider hereditary hemochromatosis (HH) → see Box 54.5
Cirrhotic liver with cholestasis
Consider progressive familial intrahepatic cholestasis (PFIC), Wilson disease, Alagille syndrome, A1AT deficiency → see Box 54.1
Cirrhotic liver without cholestasis
Consider GSD type III and GSD type IV → see Box 54.3
Consider HH → as above
The differential diagnosis of cholestatic disease in childhood is extremely broad and includes extrahepatic biliary obstruction (EHBA, choledochal cyst), infections, immune regulatory defects such as Langerhans cell histiocytosis, genetic disorders, metabolic disorders, total parenteral nutrition (TPN) and toxin exposures (see Table 54.1 ). Liver biopsies to determine the cause of cholestasis should be performed only after completion of a thorough radiologic and laboratory workup, including ultrasonography, hepatobiliary scintigraphy, viral serology, Pi typing for A1AT deficiency, and sweat chloride testing to rule out the more common causes of cholestasis in this age group.
When confronted with a predominantly cholestatic pattern of liver injury in a biopsy specimen, a useful starting point is the serum level of γ-glutamyltransferase (GGT) ( Box 54.1 ). Serum levels of GGT, a canalicular membrane protein, are usually low in disorders of defective bile acid synthesis or bile salt secretion. These entities ( Table 54.9 ) are discussed later in the chapter. Although the histologic features differ among some of these entities (e.g., lack of giant cells in progressive familial intrahepatic cholestasis type 1 [PFIC1] compared with PFIC2 and PFIC3), ultrastructural examination, specialized enzymatic assays, and genetic testing are crucial in diagnosing these disorders. Among the cholestatic disorders with normal or low serum GGT, congenital defects in bile acid synthesis are commonly diagnosed by urinary mass spectrometry. Peroxisomal biogenesis disorders, such as Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum disease, typically manifest with cholestasis, necrosis, and siderosis. These disorders are caused by mutations in multiple peroxin (PEX) genes and are usually diagnosed by measurement of very-long-chain fatty acids in plasma and erythrocyte plasmalogen.
|Disorder||Gene||Protein||Inheritance||Secondary Pattern||Confirmatory Testing|
|Progressive Familial Intrahepatic Cholestasis (PFIC) Syndrome|
|PFIC1 (allelic disorder: BRIC) |
|ATP8B1||ATPase, class I, type 8B, member 1||AR||Cirrhotic||Gene sequencing|
|ABCB11||ATP-binding cassette, subfamily B, member 11||AR||Hepatitic |
|ABCB4 (MDR3)||ATP-binding cassette, subfamily B, member 4||AR||Cirrhotic||Serum LPX, genotyping|
|Congenital Bile Acid Synthetic (CBAS) Defects|
|HSD3B7||3β-Hydroxy-Δ -C 27 -steroid dehydrogenase||AR||Hepatitic||Blood spot ESI-MS or urine MS|
|AKR1D1||Δ -3-Oxosteroid 5β-reductase||AR||Hepatitic |
|Blood spot ESI-MS or urine MS|
|North American Indian childhood cirrhosis |
|CIRH1A||Cirhin||AR||Cirrhotic||R565W (c.1741C→T) genotyping|
|Alagille syndrome |
(OMIM 118450; 610205)
|JAG1; NOTCH2||Jagged1; Notch-2||AD||Cirrhotic |
|Niemann-Pick disease type C |
(OMIM 257220, 601015)
|NPC1; NPC2||Niemann-Pick disease types C1 and C2||AR||Hepatitic |
|Filipin staining in fibroblasts|
|Peroxisomal Biogenesis Disorders|
|Zellweger syndrome |
|PEX genes||Peroxisomal biogenesis factors||AR||Hepatitic |
|↑ Plasma VLCFA by GC|
|Neonatal adrenoleukodystrophy |
|PEX||Peroxisomal biogenesis factors||AR||—||↑ Plasma VLCFA by GC|
|Infantile Refsum disease |
|PEX||Peroxisomal biogenesis factors||AR||—||↑ Plasma VLCFA by GC|
Two rare disorders of ductal plate malformation—congenital hepatic fibrosis and Caroli disease—deserve mention here. Both manifest with cholestasis and cholangitis but often with portal hypertension. Both are associated with autosomal recessive polycystic kidney disease (ARPKD), and both carry mutations in PKHD1 (fibrocystin), the that is gene defective in ARPKD, in approximately 30% of cases.
A steatotic pattern of injury is present when there is a prominent and diffuse distribution of fat vacuoles within hepatocytes. Steatosis is a common histopathologic finding in several types of inherited disorders that affect the liver; those in which other histologic features predominate are discussed separately. When one is considering the differential diagnosis of a primary steatotic pattern of liver injury, the most useful feature is the type of fat accumulation: microvesicular, macrovesicular, or mixed microvesicular and macrovesicular ( Box 54.2 ).
Microvesicular steatosis results from perturbation of mitochondrial metabolism, fatty acid β-oxidation (FAO), or electron transport chain function, through either genetic defect or drug-induced inhibition of the pathways. The latter mechanism may result from a variety of drugs, including aspirin, ibuprofen, valproate, and zidovudine (see Chapter 48 for details on Reye syndrome). The diagnostic workup of genetic defects in FAO or electron transport chain function is often based on the clinical presentation and relies on specialized biochemical and metabolic testing of plasma, urine, and biopsied muscle tissue. Pathologic features in liver biopsy specimens, such as microvesicular steatosis, cholestasis, fibrosis, cirrhosis, abnormal mitochondrial ultrastructure, and immunohistochemical demonstration of mitochondrial enzyme deficiency, support the diagnosis. Fresh-frozen liver is essential for specialized biochemical and genetic assays, particularly for analysis of the ratio of mitochondrial DNA (mtDNA) to nuclear DNA by Southern blotting (used for diagnosis of mtDNA depletion syndrome). Also, histologic examination of the liver is highly relevant in the postmortem examination of patients with suspected mitochondrial disorders.
Diffuse macrovesicular steatosis or mixed microvesicular and macrovesicular steatosis can develop in several inherited and acquired conditions ( Table 54.10 ). Two inborn errors of carbohydrate metabolism, galactosemia and hereditary fructose intolerance, are classically associated with steatosis in newborns and infants. Galactosemia is diagnosed through urine biochemical testing and red cell enzyme assays. A liver biopsy, if performed, shows macrovesicular steatosis with fibrosis and cirrhosis. A liver biopsy is indicated in hereditary fructose intolerance for confirmatory aldolase B enzyme assays on fresh-frozen tissue, although molecular assays to detect ALDOB mutations are now available. The pathologic features mimic those of galactosemia, except that cirrhosis is usually absent. Steatosis, with or without biliary cirrhosis, is common in cystic fibrosis (CF). Liver disease is relatively uncommon in young patients with CF but can lead to significant morbidity. In patients in whom the diagnosis was confirmed by positive sweat chloride testing and mutations in the cystic fibrosis transmembrane conductance regulator gene ( CFTR ), the diagnosis is suspected when eosinophilic material is present within bile ducts in liver biopsies.
|Disorder||Gene(s)||Protein(s)||Inheritance||Secondary Pattern||Confirmatory Testing|
|FAO disorders, ETC disorders, mtDNA depletion syndrome, etc.||Multiple |
ACADM, ACADL, etc.
|Multiple||Mostly AR||Plasma acylcarnitine and gene sequencing|
|Inborn Errors of Carbohydrate Metabolism|
|Hereditary fructose intolerance |
|ALDOB||Aldolase B||AR||Cholestatic||Liver enzyme activity and sequencing|
|GALT||Galactose-1-phosphate uridyltransferase||AR||Cirrhotic||RBC GALT assay|
|Cystic fibrosis |
|CFTR||Cystic fibrosis transmembrane conductance regulator||AR||Hepatitic |
|Sweat chloride, gene sequencing|
Organic acidurias and urea cycle disorders may occasionally demonstrate steatosis or focal glycogenosis, but these disorders are diagnosed through urine chromatographic analyses. In some cases, progression to fibrosis and even cirrhosis may occur. Other disorders may demonstrate steatosis as a secondary feature. Biopsies of glycogen storage disease (GSD) types I and III often reveal steatosis. The liver in Wilson disease may be steatotic, but the predominant pattern is hepatitic or cirrhotic or both.
A storage pattern is characterized by the presence of enlarged, swollen, and pale hepatocytes and/or reticuloendothelial cells, including Kupffer cells and portal macrophages. The stored material results from specific enzyme deficiencies in various metabolic pathways. A diverse group of disorders (>30) result in the development of a storage pattern within the liver, most of which cause hepatomegaly (see Table 54.8 ). Most, but not all (e.g., not the X-linked disorders, Fabry disease, or Hunter disease), are inherited in an autosomal recessive fashion. These disorders often demonstrate variable penetrance and expressivity, with different clinical and histologic manifestations among family members with the same genetic defect. For a comprehensive discussion of these disorders, readers are referred to several excellent review articles.
For pathologists confronted with biopsy specimens revealing a storage pattern, the most efficient approach is one that involves a pediatric geneticist and a clinical biochemist, because the patient’s clinical presentation and laboratory findings often suggest the most likely diagnosis. The storage pattern can be subclassified as either lysosomal or cytoplasmic. Because reticuloendothelial cells are rich in lysosomes, Kupffer cells and histiocytes are typically more involved in lysosomal storage diseases than in disorders with cytoplasmic storage (e.g., GSD types I, III, and IV). However, this distinction is not absolute, because diffuse hepatic and extrahepatic involvement of the reticuloendothelial system is a well-documented feature in some GSDs, particularly GSD type IV. Distinguishing lysosomal (membrane-bound) from cytoplasmic storage disorders by electron microscopy is, therefore, quite useful.
Hepatic involvement in Pompe disease (GSD type II) is variable. The liver architecture is usually intact. PAS-positive diastase-sensitive inclusions are present within histiocytes and hepatocytes ( Box 54.3 ). Diagnostic confirmation is usually established by measurement of acid α-glucosidase activity in muscle or fibroblasts. Additional confirmation can be done by GAA gene sequencing.
The differential diagnosis of cytoplasmic storage disorders includes GSD types I, III, IV, VI, and IX ( Table 54.11 ). These disorders are discussed later in this chapter.
|Disorder||Inheritance||Gene||Protein||Storage Material||Liver Histology||Other Features||Ultrastructure||Diagnostic Testing|
|GSD Ia (von Gierke disease)||AR||G6PC||Glucose-6-phosphate, catalytic subunit||Glycogen||PAS+, diastase-sensitive cytoplasmic glycogen||−||Steatosis, adenomas, HCC||−||Fresh liver enzyme activity, genetic testing|
|GSD Ib||AR||SLC37A4||Glucose-6-phosphate transporter|
|GSD II (Pompe disease)||AR||GAA||Acid α-glucosidase||Glycogen||PAS+ vacuoles||−||−||Membrane-bound monoparticulate glycogen||Fibroblast and/or muscle enzyme activity, genetic testing|
|GSD III||AR||AGL||Glycogen debranching enzyme||Glycogen||PAS+, diastase-sensitive cytoplasmic glycogen||−||Steatosis, cirrhosis, HCC||−||Fresh liver or muscle enzyme activity, genetic testing|
|GSD IV (Andersen disease)||AR||GBE1||Glycogen debranching enzyme||Glycogen||PAS+, diastase-sensitive cytoplasmic glycogen||Kupffer cell inclusions±||Cirrhosis, HCC||Amylopectin-like cytoplasmic glycogen||Fresh liver or fibroblast enzyme activity, genetic testing|
The differential diagnosis of lysosomal storage disorders with foamy histiocytes includes lipidoses ( Table 54.12 ), chiefly Gaucher disease, Farber disease, Niemann-Pick disease (NPD) types A and B, GSD type II, mucopolysaccharidoses, and GM1 gangliosidosis. In Gaucher disease, the most common lysosomal storage disorder, there is a characteristic diffuse infiltration by engorged histiocytes (Gaucher cells) containing PAS-negative cytoplasmic (“crinkled-paper”) inclusions of glucosylceramide. Hepatocytes are typically spared. On demonstration of tubular structures by electron microscopy, one should, for confirmation, measure the level of leukocytic or fibroblastic acid β-glucosidase activity and sequence the GBA gene for mutations.
|Disorder||Inheritance||Gene||Protein||Storage Material||Liver Histology||Other |
|Gaucher disease||AR||GBA||Acid β-glucosidase||Glycosylceramide||−||Gaucher cells (20-100 µm): eosinophilic corrugated “crinkled-paper” cytoplasm||Fibrosis, rarely cirrhosis||Spindled tubular structures||Enzymes activity (l, f) ± GBA mutations|
|Niemann-Pick disease types A and B||AR||SMPD1||Acid sphingomyelinase||Sphingomyelin||Vacuolated hepatocytes||Niemann-Pick cells (25-75 µm): foamy histiocytes, lipofuscin+||ORO+, LXB+, PAS−||Laminated myelin-like figures||Enzymes activity (l, f)|
|Niemann-Pick disease type C||AR||NPC1 |
|NPC1, NPC2||Cholesterol||Cholestasis, giant cell transformation||Sea-blue histiocytes||Cirrhosis||Whorled aggregates||Filipin staining (f) + NPC1, NPC2 mutations|
|Farber disease||AR||ASAH1||Acid ceramidase||Ceramide||−||Lipogranulomas, foamy histiocytes||Fibrosis||Curvilinear Farber bodies||Enzymes activity (l, f, p)|
|GM1 gangliosidosis||AR||GLB1||β-galactosidase 1||Glycosphingolipids||Vacuolated hepatocytes||Finely vacuolated||Fibrillogranular material||Enzymes activity (l, f, p)|
|Wolman disease |
|AR||LIPA||Acid liposomal lipase||Cholesterol esters||Microvesicular droplets||Enlarged vacuolated, periportal foamy histiocytes||ORO+, cirrhosis, |
|Cholesterol crystal profiles||Enzymes activity (l, f) + LIPA mutations|
Hepatitic pattern, in infants, refers to a histologic pattern that reveals hepatocyte unrest with or without necrosis, diffuse giant cell transformation of hepatocytes, extramedullary hematopoiesis, and prominent cholestasis (see Table 54.6 ). In older children, portal, interface, or lobular inflammation (or some combination of these) is typically present, but usually without cholestasis. Chief among the inherited disorders that manifest with a hepatitic pattern are A1AT deficiency and Wilson disease. A number of other inherited disorders with characteristic histologic patterns of injury (e.g., NPD type C, Alagille syndrome with cholestasis) can also manifest with a superimposed hepatitic pattern on liver biopsies. These entities are discussed later in this chapter.
When investigating biopsy specimens with a hepatitic pattern for a suspected inherited disorder, it is crucial to rule out acquired causes of hepatitis (e.g., infection, toxin or drug exposure, TPN) that are far more common in this age group. It is also important to evaluate the clinical presentation and laboratory results. For example, A1AT deficiency liver disease can manifest either in the neonatal period with hepatitis or later in childhood with cirrhosis, but clinical manifestations of Wilson disease are rare before the age of 5 years (see Table 54.2 ). On biopsy, the presence of PAS-positive, diastase-resistant inclusions within zone 1 hepatocytes is characteristic of A1AT deficiency, but immunostaining is more sensitive and more specific. Serum A1AT phenotyping by isoelectric focusing (Pi typing) is the confirmatory assay for diagnosis of A1AT deficiency in cases of suspected neonatal hepatitis, and it is particularly valuable in cases that mimic EHBA (i.e., bile duct proliferation, no biliary excretion on scintigraphy). Diagnosis of Wilson disease is less straightforward; screening for decreased serum ceruloplasmin levels (<20 mg/dL) can be problematic, because both decreased (hypoplasminemia or aceruloplasminemia) and elevated levels (acute phase reaction) may be seen in other conditions ( Box 54.4 ). A low serum alkaline phosphatase level may be a useful clue to the etiology, as well as increased unconjugated bilirubin, which reflects hemolysis in children with acute liver decompensation.
Cirrhosis, an end-stage response to chronic liver injury, is common to several different types of inherited disorders. Therefore, the differential diagnosis of liver biopsies with a cirrhotic pattern rests largely on the presence or absence of other characteristic microscopic findings ( Box 54.5 ). Metabolic disorders that lead to cirrhosis also carry an increased risk of neoplasia. Advanced stages of congenital hepatic fibrosis (discussed earlier) may be confused with cirrhosis; however, bile duct ectasia is a characteristic feature of the former. Although mitochondrial hepatopathies may lead to several different patterns of liver injury, it is most often steatosis. Less often, these disorders may manifest with hepatitis and cirrhosis.
Tyrosinemia, caused by a deficiency of fumarylacetoacetate hydrolase, can lead to cirrhosis in early life (infancy), hepatic failure, hepatocellular necrosis, or giant cell hepatitis.
Hereditary hemochromatosis (HH) is caused by mutations in HFE , the hemochromatosis gene, and leads to cirrhosis and hepatocellular carcinoma (HCC). Although the defect in iron metabolism is present at birth, the clinical manifestations of HH are rarely apparent before adulthood, when long-term effects of chronic iron overload typically manifest (see later discussion).
Several types of inherited disorders predispose the child to the development of focal nodular hyperplasia, hepatic adenoma, and HCC. In contrast, hepatoblastoma, the most common malignancy in the liver of children, is not usually associated with inherited metabolic disorders, although trisomy 18, neurofibromatosis, and congenital hepatic fibrosis have been linked to hepatoblastoma. The increased risk for HCC is chiefly caused by the development of cirrhosis, but HCC can arise in noncirrhotic patients with A1AT deficiency, hemochromatosis, or GSD type I. The histologic features and biologic behavior of HCC and adenomas arising in patients with a metabolic disorder are similar to those of neoplasms that arise in cirrhosis resulting from other causes. Cirrhosis and neoplasms that arise in inherited metabolic disorders are indicative of advanced disease (not necessarily advanced age), and the diagnostic features of the underlying disorder can usually be identified in non-neoplastic areas of the liver tissue ( Box 54.6 ).
Most patients with GSD type I have hepatic adenomas by 15 years of age, although adenomas may be present in early childhood. Dysplastic changes and HCC within individual adenomatous nodules have also been reported in this condition.
Among all of the metabolic disorders of the liver, hereditary tyrosinemia (discussed later) carries the highest risk for development of HCC (13% to 15% incidence). Typically, hepatocellular dysplasia and foci of HCC develop in a background of mixed micronodular and macronodular cirrhosis, but treatment should begin in infancy to abort the mutagenic process. Not all infants manifest overt liver dysfunction with time.
The incidence of HCC in patients with HH (discussed later) is approximately 10%. Most cases develop in a background of cirrhosis. Because of the widespread availability of testing for the HFE gene mutations C282Y and H63D and sensitive transferrin-iron screening tests, a biopsy diagnosis is required only in cases with a negative genotype or high ferritin levels.
Other inherited disorders that are less commonly associated with HCC include A1AT deficiency, PFIC2, Wilson disease, Alagille syndrome, and GSD types I, III, and IV. The characteristic biopsy features were described earlier. A1AT deficiency is a precursor to HCC. In some cases, PiZ heterozygotes were found to have HCC (and cholangiocarcinoma) in noncirrhotic livers. Fanconi anemia, Familial adenomatous polyposis and Beckwith-Weidemann syndrome are other syndromes that predispose to cancer. Three percent of patients with Fanconi anemia develop adenomas or HCC, and hepatoblastoma has a well-known association with both familial adenomatous polyposis and Beckwith-Weidemann syndrome. Finally, cholangiocarcinoma is a rare complication of congenital hepatic fibrosis. This tumor was recently described in two children with PFIC2.
Liver Diseases of Infancy
Although sudden death within 2 to 3 days after birth is usually caused by nonmetabolic conditions such as sepsis or congenital heart disease, some inborn errors of metabolism are also associated with acute life-threatening illness ( Box 54.7 ). Defects of FAO lead to cardiac arrhythmias and can cause sudden death (see Mitochondrial Cytopathies ). At autopsy, excess droplets of fat may be present in the liver and heart of patients with a defect of FAO. If a disorder of FAO is suspected, tissue specimens should be obtained as soon as possible after death, before autopsy, for metabolic testing ( Table 54.13 ). Both liver and muscle tissue should be obtained for analysis. In addition, urine and cerebrospinal fluid should be snap-frozen and stored for further analysis. Blood spots should be obtained for analysis of acylcarnitines. Whole blood specimens should be placed in an ethylenediaminetetraacetic acid (EDTA) tube for DNA extraction and in a lithium heparin tube (spun and separated within 20 minutes of collection) for metabolite analysis. A full-thickness skin biopsy should be performed under sterile conditions within 12 hours of death for fibroblast culture and archiving.
Congenital lactic acidurias
Pyruvate oxidation defects
Krebs cycle defects
Respiratory chain defects
Mitochondrial fatty acid β-oxidation disorders
Defects of membrane-bound enzymes
Defects of matrix enzymes
Urea cycle defects
Amino acid disorders
Maple syrup urine disease
Molybdenum cofactor deficiency
|Collect||Blood, urine, CSF, vitreous humor (dodecanoic acid = MCAD deficiency) |
Bile (carnitine and acylcarnitines = FAO disorders)
|Freeze||Liver, skeletal, cardiac muscle|
|Sample for cell culture||Skin fibroblasts (DNA and enzyme analyses)|
Sudden and unexplained death in an infant or young child is often the first manifestation of medium chain acyl-coenzyme A dehydrogenase (MCAD) deficiency, the most common FAO disorder. MCAD deficiency manifests with hepatomegaly and steatosis and may be confused with Reye syndrome. A particular Lys304Glu mutation in the ACADM gene is highly prevalent in some populations. Since the institution of newborn screening, early diagnosis has led to prospective management of acute episodes of hypoketotic hypoglycemia.
Neonatal hemochromatosis, also termed neonatal iron storage disease, is a rare syndrome that is characterized by the presence of congenital cirrhosis and fulminant liver failure. This condition exhibits abundant iron deposition in the liver and in other organs, but not in the spleen or bone marrow. Clinically, patients with neonatal hemochromatosis, either before birth or shortly thereafter, exhibit liver failure, including hypoglycemia, coagulopathy, hypoalbuminemia, ascites, and hyperbilirubinemia. Although some infants recover with exchange transfusion and some survive to transplantation, most die of their disease.
Neonatal hemochromatosis has been described in association with various conditions, including metabolic disorders (tyrosinemia, Δ -3-oxosteroid 5β-reductase deficiency, mtDNA mutations, and Zellweger syndrome), infections (echovirus 9, cytomegalovirus [CMV], herpes simplex virus, rubella, and parvovirus B19), and karyotypic disorders (Down syndrome). As a result, some authors regard neonatal hemochromatosis as a final common phenotype of any gestational insult that culminates in abnormal iron metabolism. At least three patterns of disease transmission have been described: transmission of maternal alloantibodies, autosomal recessive inheritance, and matrilineal inheritance. In the last instance, several reports have documented women with more than one affected child, but the children were fathered by different men. Although gonadal mosaicism in these mothers has not formally been excluded, the possibility of mitochondrial inheritance also has not been excluded. Neonatal hemochromatosis is not associated with mutations in the HFE , the gene involved in most cases of HH (see later discussion).
In 2004, Whitington and Hibbard first reported giving high-dose intravenous γ-globulin to pregnant women with a history of a previously affected infant, and this treatment prevented recurrence in a small series. Their findings have since been confirmed in many centers, and it is now imperative to determine the etiology of all perinatal forms of acute liver injury. Mimicry of hemochromatosis has been seen in cases of mtDNA depletion and other circumstances, which presumably do not benefit from intravenous immunoglobulin therapy.
The antibody responsible for neonatal hemochromatosis has yet to be determined. Complement fixation induced by immunoglobulin G of maternal origin is detected by immunofluorescence for the membrane attack complex on hepatocytes. One patient with cirrhosis at birth did not have hemosiderosis and survived without specific therapy. However, the usual scenario is fatal necrosis with extensive parenchymal siderosis without reticuloendothelial iron, suggesting dysfunction of macrophages. This has been observed even prenatally: Three of eight stillborn or very premature infants had no extrahepatic siderosis. Recently, Whitington and colleagues have provided insight into the severe degree of parenchymal siderosis that accompanies the hepatocellular injury. The injured livers have significantly reduced hepcidin, hemojuvelin, and transferrin gene expression compared with normal livers.
Antibodies to mitochondrial proteins are responsible for primary biliary cirrhosis, a disease that affects women disproportionately. Two patients transmitted this disease transplacentally to their infants, producing transient liver injury. One infant was born with ascites and conjugated hyperbilirubinemia. In the other, the presentation was more insidious. His biopsy, at 5 weeks, showed portal inflammation involving bile ducts and ductules and mild portal fibrosis, as well as multinucleated giant hepatocytes typical of neonatal hepatitis. Immunofluorescence was able to detect immunoglobulin G deposits surrounding hepatocytes. Within 3 months, both infants showed no evidence of liver dysfunction, and the antibodies were undetectable.
Neonatal hemochromatosis resembles neonatal hepatitis in infants with systemic lupus erythematosus, in which the mother has high titers of antinuclear anti Ro (SSA) and anti La antibodies.
The liver in patients with neonatal hemochromatosis (usually seen at postmortem examination) reveals cirrhosis and cholestasis ( Fig. 54.2 ). Confluent areas of hepatocellular loss and a variable degree of hepatocyte regeneration are typical. Residual hepatocytes may demonstrate giant cell or pseudoacinar transformation. Iron deposition is typically coarsely granular and located predominantly within hepatocytes, sparing Kupffer cells. Extrahepatic sites of siderosis include the parenchymal cells of the heart, thyroid, pancreas, adrenal glands, kidneys, and the submucosal glands of the gastrointestinal and upper respiratory tracts.
Although neonatal hemochromatosis carries a high risk of death, it remains in the differential diagnosis of severely ill neonates who survive beyond the first days of life. Demonstration of siderosis in biopsy samples from oral submucosal glands is a rapid diagnostic method. T2-weighted magnetic resonance imaging can be used to assess the presence of iron in various tissues. Siderosis of the liver and extrahepatic organs may also accompany other conditions, such as erythropoietic disorders, sickle cell disease, thalassemia, and erythroblastosis from blood group incompatibility. However, hemosiderosis affects the reticuloendothelial system primarily. These other diseases need to be excluded by other clinical and laboratory studies.
Heritable disorders of bilirubin conjugation can rarely produce liver dysfunction (see later discussion). Liver diseases of infancy most often manifest with jaundice owing to conjugated hyperbilirubinemia. This occurs because of the relative immaturity of hepatic secretory and excretory functions in early life. Some of the disorders of infancy that cause neonatal jaundice are listed in Table 54.1 . In all cases of neonatal jaundice, the possibility of EHBA or hepatic damage due to drug exposure (including inadvertent drug overdose) should be excluded. Infants requiring TPN are at risk for cholestatic liver disease (see Chapter 48 ). Infectious causes of liver disease in infancy include enterovirus, parvovirus B19, and adenovirus, which cause direct cytopathic cell death, as well as bacterial sepsis, urinary tract infection, and intrauterine exposure to maternal infections (of the “TORCH” acronym), all of which cause liver damage to neonates and infants (see Chapter 46 ). Acquired syphilis is an exceedingly uncommon cause of perinatal liver disease.
Inherited metabolic disorders of carbohydrate, amino acid, and lipid and glycolipid metabolism, along with disorders of the biosynthetic and secretory pathways for bile acids, should always be considered in the differential diagnosis of neonatal jaundice (see Table 54.6 ). Storage of abnormal A1AT and abnormal function of the CFTR compromise hepatic formation of bile. Defects in the transporters responsible for bile formation give rise to progressive familial intrahepatic cholestasis. Inherited defects of peroxisomal and mitochondrial function can cause neonatal jaundice. Shock may cause cholestatic liver damage in neonates. Alagille syndrome may manifest in early infancy as “giant cell hepatitis”; it can mimic biliary atresia and may lead to Kasai portoenterostomy (KPE). The nonspecific designation of “neonatal hepatitis/giant cell hepatitis” applies to the 25% of patients in which a specific etiology for neonatal jaundice remains undetermined.
Extrahepatic Biliary Atresia
EHBA accounts for more than 30% of all cases of cholestasis in a neonate. This disorder has an incidence of 1 in 8000 to 18,000 live births. Most cases are sporadic and do not reveal a positive family history of neonatal cholestasis. There is one report of a 20-year-old mother who underwent a portoenterostomy for EHBA at 64 days of age and subsequently gave birth to a daughter with EHBA. In contrast, in only 2 of 30 sets of twins were both infants affected, and both pairs were dizygotic, whereas none of the 7 monozygotic pairs displayed concordance. However, there are rare exceptions. Variation in epigenetic modifications of genomic DNA has been suggested for this developmental difference. Infants with biliary atresia are typically of normal gestational age and birth weight. However, the increasing detection of biliary cysts in midgestation, via ultrasonography, indicates that as many as 10% of patients with EHBA have very early onset. The pathology in those cases is not notably different that in other patients with EHBA.
Cholestatic jaundice is the main clinical presentation. It typically develops in the first few weeks of life and does not remit, unlike the mild physiologic jaundice of early infancy. Furthermore, in physiologic jaundice, the mildly elevated serum bilirubin is primarily unconjugated, and the serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are normal. The progressive biliary obstruction that characterizes biliary atresia leads to a progressive rise in serum bilirubin levels in which conjugated bilirubin represents 50% to 80% of the total. A recent study of conjugated or direct-reacting bilirubin in the first 48 hours of life revealed significant elevations in all infants with EHBA compared with aged-matched controls, even though the total bilirubin level was not increased. Serum levels of GGT are increased several times above normal. Liver biosynthetic function, as indicated by serum albumin levels and prothrombin time, is usually normal at initial presentation.
In all suspected cases, ultrasonography should be performed to exclude the presence of an extrahepatic biliary tract anomaly, such as a choledochal cyst. Hepatobiliary scintigraphy is also useful to assess the status of biliary tract function, but in many hepatocellular diseases of infants, there is also an absence of excretion of the labeled molecule into the intestine. Percutaneous liver biopsy is used to determine whether there is histologic evidence of large bile duct obstruction. Biopsy features of atresia may also occur with other extrahepatic forms of biliary obstruction ( Box 54.8 ).
Extrahepatic Biliary Obstruction Without Atresia—Rare Events in Infancy
Spontaneous perforation of bile duct
Bile plug syndrome
Segmental cystic dilatation of biliary ducts
Duodenal atresia (more common in Down syndrome)
Peptic ulceration secondary to duplication of intestine
Compression by enlarged lymph node
Hemangioendothelioma and other neoplasms of head of pancreas
Extrahepatic Obstruction—Liver Histology
Portal tract and periportal fibrosis
Bile duct and ductular proliferation
Bile duct “thrombi” or plugs
±Persistent extra-medullary hematopoiesis
Beware of α 1 -antitrypsin, timing of biopsy
The overall accuracy rate of percutaneous liver biopsy for diagnosis of EHBA is 79% to 95%. The decision to proceed with a biliary tract exploratory surgical procedure does not rest solely on the pathologic findings in a liver biopsy specimen. For instance, the presence of acholic stools, an undetectable or irregular contour of the gallbladder on sonographic studies, and the findings of retrograde endoscopic choledochography are also used to diagnose biliary atresia clinically.
Potential mechanisms of biliary atresia include a defect in hepatic morphogenesis, a defect in prenatal hepatic circulation, immunologic dysregulation in the perinatal period, intrauterine or perinatal viral infection, and toxin exposure ( Table 54.14 ). These hypotheses have been put forth on the basis of epidemiologic studies and molecular analyses of tissue specimens from human patients. Mouse models of biliary atresia have provided some additional clues. A growing consensus is that the pathogenesis in most cases probably involves an infectious or immune-mediated fibro-obliteration of the extrahepatic and intrahepatic biliary tract. Defective morphogenesis of the biliary system may be the cause in the remainder of cases.
|Proposed Mechanisms||Classic versus Syndromic Presentations||Associated Malformations|
In favor of the first hypothesis are the finding of an association between biliary atresia and several viral agents (CMV, reovirus, rotavirus) and the ability of viruses introduced into neonatal mice to cause inflammatory destruction of the bile ducts. Studies of human liver specimens at different phases of disease progression point to the presence of a proinflammatory commitment of lymphocytes with a predominant type 1 helper T cell (Th1) phenotype. Prevention of experimental inflammatory destruction of bile ducts occurs in mice that are deficient in interferon-γ. Neonatal systemic lupus can mimic biliary atresia. Molecular profiling of liver tissue from children with biliary atresia has revealed a unique proinflammatory footprint related to activation of lymphocytes, particularly natural killer cells.
The initial biopsies of 47 infants with biliary atresia showed overexpression of genes associated with inflammation or fibrosis or both. Not surprisingly, the patients with a fibrosis signature were older and had decreased duration of transplant-free survival. When serum samples collected at the same time from 19 infants with EHBA and 19 with other forms of neonatal cholestasis were subjected to gel electrophoresis and tandem mass spectrometry, a combination of 11 proteins was able to discriminate between the two groups. Among them were apolipoproteins CII and E, whose genes on chromosome 19 are regulated by farnesoid X receptor, which in turn is responsive to bile acids. Other clues to the pathogenesis of EHBA from this study were upregulation of proinflammatory “positive” acute phase reactants, such as complement C3, and a relatively reduced level of “negative” acute phase proteins such as prealbumin.
Prompted by the similarities between biliary duct inflammation and graft-versus-host disease, Suskind and colleagues were the first to describe maternal “microchimerism” in the livers of infants with biliary atresia. Fluorescence in situ studies found two to four lymphocytes per tissue section to be XX in seven of eight affected boys. By quantitative polymerase chain reaction, between 1 and 142 copies of maternal DNA were detected for every 25,000 copies of neonate DNA. This was further documented in 14 more boys with EHBA by Hayashida and Muraji and their associates, although control subjects without biliary atresia also had a few XX lymphocytes in these studies. CD8+ T cells were especially more abundant in the EHBA biopsies in the latter study. Human leukocyte antigen (HLA) class I matching was significantly more prevalent in 57 maternal-child pairs with biliary atresia than in 50 control pairs (odds ratio, 2.46), possibly providing for greater survival of the chimeric lymphocytes.
In favor of the second hypothesis are data that show a systemic dysregulation of morphogenesis in patients with biliary atresia, such as the coexistence of nonhepatic embryologic abnormalities, evidence for abnormal development of the ductal plate of the maturing intrahepatic biliary tract, and overexpression of certain regulatory genes in children who have an early form of biliary atresia. Associated developmental abnormalities include polysplenia or asplenia, cardiovascular defects, abdominal situs inversus, intestinal malrotation, and anomalies of the portal vein and hepatic artery in 25% of patients (see Table 54.14 ).
Mutations in the laterality genes CFC1 and ZIC3 lead to laterality defects and biliary atresia in some patients. The Inv mouse that develops situs inversus also develops biliary obstruction. The JAG1 gene has also been implicated in the pathogenesis of biliary atresia, because affected patients with a poor outcome also show a high frequency of JAG1 single nucleotide polymorphisms. The persistent expression of HES1 protein in the nuclei of biliary epithelial cells specimens of biliary atresia obtained up to 3 months after birth offers more evidence for disorderly Notch signaling in this disease. In normal development, such expression is silenced by 16 weeks’ gestation.
The cystic bile ducts detected by prenatal ultrasonography may or may not be associated with biliary atresia. Among 88 patients with atresia, Okada and co-workers found a better prognosis for those with common duct atresia, as expected, but no association with other malformations despite early fetal onset. Therefore, the concept of a “fetal” (i.e., developmental) versus an acquired variant of biliary atresia was challenged. Sequential imaging starting at 16 weeks’ gestation revealed disappearance of a cyst before birth and extreme narrowings of the common hepatic duct at 30 days after birth.
The ciliopathies responsible for polycystic disease and congenital hepatic fibrosis (discussed later) may have a new and potentially meaningful relationship to biliary atresia. Other ciliary dysfunction contributes to laterality defects in embryonic development, including syndromic biliary atresia. Having observed a twofold greater incidence of renal cysts developing in children after transplantation for EHBA versus other liver diseases, Hartley and colleagues found two other examples in long-term survivors. Using immunohistochemistry, they found that expression of fibrocystin was missing in the biliary epithelium of the EHBA patients, suggesting a role for PKHD1 or genes involved in primary ciliogenesis in this disease. Chu and associates showed, for the first time, that the cilia in biliary epithelium of five affected children were fewer, shorter, and abnormally oriented. Two other patients with biliary atresia who had no other malformations displayed alterations similar to those in epithelium of patients with other cholestatic diseases. Therefore, the defects may be secondary and nonspecific.
An all-encompassing hypothesis is that a genetically susceptible individual undergoes inflammatory destruction of the extrahepatic biliary system in response to as yet undetermined environmental factors.
A diagnosis of EHBA is favored if a liver biopsy specimen exhibits bile ductular proliferation (neocholangioles), portal edema, and fibrosis but lacks sinusoidal fibrosis. Neutrophilic cholangitis and pericholangitis may or may not be present. The presence of bile plugs within bile duct lumina (which are distinct from the lumina of neocholangioles at the margins of portal tracts) and increased numbers of bile duct profiles are helpful diagnostic findings ( Fig. 54.3 ). Fifteen percent of cases show giant cell transformation of hepatocytes ( Fig. 54.4 ). The ductular reactions seen in cases of obstruction, as opposed to those that accompany hepatocellular necrosis due to toxins or ischemia, have been extensively analyzed by Desmet for many years. He hypothesized that the proliferation of duct epithelium with elongation and branching is controlled by molecular interactions with regional fibroblasts and represents an adaptive response to enhanced recycling of bile acids. The ductular “metaplasia” observed in other circumstances is attributed to the capacity of preexisting liver precursor cells in the canal of Hering to assume a hepatocellular or ductular phenotype and to the newly appreciated capacity of mature cells to “differentiate” and “redifferentiate” in vivo. Evidence for epithelial-mesenchymal transition as a mechanism for progressive fibrosis in EHBA has also been provided.
The classic “obstructive” findings of bile duct proliferation and inspissated bile plugs are not always the result of atresia (see Box 54.8 ). Some cases may show nonclassic features such as prominent portal tract arteries and an absence of bile duct proliferation ( Fig. 54.5, A and B ). In keeping with the developmental theory of biliary atresia, a subset of affected patients exhibit ductal plate malformation (see Fig. 54.5, C ). Recapitulating immature fetal portal tracts, this latter entity consists of portal tracts without an interlobular bile duct but with a centrally located hepatic artery and a peripheral rim of bile ductular structures. However, this phenomenon is not limited to the 20% to 25% of patients with a laterality defect (biliary atresia splenic malformation). As a result, EHBA can be difficult to diagnose, even for the most experienced pediatric hepatopathologist (see Fig. 54.5, D ).
On performance of a hepatoportoenterostomy, a bile duct remnant is usually submitted for pathologic examination. Typical findings in the bile duct remnant include fibrosis and obstruction of the lumen, a variable degree of periductal inflammation, and apoptotic degeneration of residual bile duct epithelium ( Fig. 54.6 ). These findings do not differ in syndromic cases of biliary atresia and those discovered by prenatal ultrasonography, supporting the concept of a shared pathogenetic pathway.
Natural History and Treatment
Before 1959, when the KPE procedure was introduced, biliary atresia was considered to be uniformly fatal by 2 years of age, with a median age at death of 10 months. After performance of a Kasai procedure, about 20% of affected infants show complete reversal of their jaundice and can lead relatively normal lives. The best survival rate in KPE patients with a native liver is 53% at 10 years, with jaundice clearing in 75% postoperatively. In the first report of the U.S. Biliary Atresia Research Consortium in 2006, a decline in total bilirubin at 3 months after KPE to less than 2 mg/dL was seen in 36.5% of children, and a good response (to <6 mg/dL) was seen in another 29%. Most patients in the excellent response group had a much better outcome. The 25% of children with a laterality defect fared more poorly, even if treated earlier. The surgical team in the study found a favorable drop in total bilirubin in 45% of patients in 2011, with a survival rate for those with a native liver of 54% at 1 year and 47% at 2 years. Atresia of the common hepatic duct or ducts at the liver hilum (Ohi types 2 and 3) had a worse prognosis than an atretic common bile duct (Ohi type 1), similar to the prognosis in patients with other malformations, ascites at surgery, or delay in surgery beyond day 75. Children operated on within the first 30 days had a 74% survival rate, with their native liver, at 2 years. At King’s College Hospital in London, 56% of infants with EHBA cleared jaundice, and the 2-year survival rate in patients with their native liver was 65%. The 51 patients with biliary atresia splenic malformation or biliary cysts tended to be operated on earlier but fared worse if the procedure was delayed. Nevertheless, the same group reported that even when surgery was performed on day 100 or even later, 45% of patients were alive with their native liver at 5 years, and 40% at 10 years, suggesting that patients may postpone transplantation by the KPE.
Infants who do not respond to the Kasai procedure suffer from recurrent episodes of ascending cholangitis or sepsis due to the immediate proximity of a bowel segment to the porta hepatis of the residual biliary tree. Regardless of the presence or absence of ascending cholangitis, the liver may progress to cirrhosis with portal hypertension. Large bile lakes may form at the hilum, indicating a persistent effort at bile secretion by hepatocytes ( Fig. 54.7 ). The pathogenesis of progressive fibrosis in chronic cholestatic diseases, including EHBA, PFIC1, PFIC2, and Alagille syndrome, has been linked to persistence of Hedgehog (Hh) signaling, which normally promotes embryonal duct differentiation and then shuts off as the liver matures. Immunohistochemical colocalization of the Hh transcription factor Gli2 and the mesenchymal markers vimentin and FSP1 in some of the reactive ductular epithelial cells in these diseases is evidence of reversal of mesenchymal-epithelial transition. Similar colocalization of FSP1 and cytokeratin 7 was shown in ductular epithelium, and this ductal cell derangement may lead to fibroplasia. Growth failure, malnutrition, deficiencies of lipid-soluble vitamins, and altered protein–energy and nutrient utilization are also potential complications.
A failed Kasai procedure in a patient with biliary atresia is the most frequent indication for liver transplantation in infants and young children. Patient survival after orthotopic transplantation for EHBA in the U.S. United Network for Organ Sharing from 1988 to 2003 was 85.8% at 10 years, with graft survival of 72.7%. Cadaveric split-liver grafts were associated with reduced survival, as was the need for life support at the time of surgery. Pathologic examination of explanted livers for occult malignancy is crucial for all forms of chronic liver disease in children.
Neonatal Sclerosing Cholangitis
In addition to neonatal sclerosing cholangitis associated with ichthyosis (OMIM 607626) due to CLDN1 mutations, several infants of consanguineous matings have been described with progressive sclerosing cholangitis from infancy. An 8-month-old Arab boy reported by Bar Meir and associates had elevated immunoglobulins and anti–smooth muscle titers, but there were no such abnormalities in his mother. These few patients serve to highlight the concept of an intrahepatic form of biliary “atresia,” but they also manifest extrahepatic ductal lesions by imaging, similar to older patients with progressive sclerosing cholangitis. Langerhans cell histiocytosis can lead to sclerosing cholangitis as part of a systemic process in young children (see Paucity of Intrahepatic Bile Ducts ) ( Fig. 54.8 ). Therefore, it may be most useful to consider that there is a continuum of inflammatory and sclerosing processes that may have a heritable basis in susceptibility and that show a variable degree of ductal obliteration.
Neonatal Hepatitis Syndrome
A neonatal hepatitis syndrome resembling biliary atresia was first described by Burns in 1817. By the mid-1950s, two distinct disease categories of cholestasis of infancy were established: biliary atresia , an inflammatory sclerosing syndrome of the extrahepatic biliary tract with hepatic features of bile duct obstruction, and neonatal hepatitis , a nonobstructive type of neonatal cholestatic syndrome with characteristic hepatitic features. At that time, neonatal cholestasis due to disorders of bile formation and transport was not yet recognized. In the subsequent decades, enormous progress was made in the molecular characterization of neonatal cholestatic disorders. This entity is now best considered a clinicopathologic syndrome in which there are many potential etiologies, including infections, anatomic or structural defects, metabolic and inherited disorders, hormonal insufficiency, and vascular, toxic, and immune causes (see Table 54.6 ).
A review of all biopsies designated neonatal giant cell hepatitis at the Johns Hopkins and University of Chicago tertiary hospitals from 1984 to 2007 found 62 cases (75% boys; average age, 2 months). Of those cases with clinical follow-up, half proved to be idiopathic. Ultimately, 8% of patients were found to have biliary atresia, 6% Alagille syndrome, 6% bile salt synthetic defects, and 16% hypopituitarism. At the Texas Children’s Hospital in Houston, 151 infants up to 3 months old were biopsied because of persistent conjugated hyperbilirubinemia. Fifty-nine percent were boys. However, among the 80 patients (53%) who were found to have extrahepatic biliary obstruction, 60% were girls. Forty-eight patients had neonatal hepatitis, with or without giant cells, one of whom proved to have CMV infection. One infant had A1AT deficiency, one hypopituitarism, one McCune-Albright syndrome, and one Langerhans cell histiocytosis. Sixteen had paucity of intrahepatic bile ducts, but none was syndromic (i.e., Alagille syndrome) at this early age. Disorders without a specific identifiable etiology now account for about 25% of the total.
Persistent unconjugated hyperbilirubinemia raises the possibility of an inherited defect in bilirubin conjugation or hemolysis. Diagnostic assessment and therapeutic intervention is then critically important to avoid kernicterus and permanent neurologic damage. In contrast, predominantly conjugated hyperbilirubinemia in newborns should prompt a rigorous diagnostic investigation for biliary atresia. An approach to the workup of neonatal hepatitis was presented earlier (see Cholestatic Pattern and Table 54.7 ).
The hallmark histologic finding of many neonatal liver disorders is the formation of large multinucleated hepatocytes (giant cells), which are part of the broader spectrum of lobular disarray in neonatal hepatitis ( Fig. 54.9 ). Nuclear inclusions in hepatocytes may suggest DNA viruses ( Figs. 54.10 and 54.11 ); those in red cell precursors may suggest parvovirus B19. In some cases, most of the liver parenchyma is transformed into giant cells, and this is referred to as “syncytial giant cell hepatitis.” When this histologic picture predominates, electron microscopy can be extremely helpful, and even pathognomonic, if NPD type C is the cause. Of 40 infants evaluated for neonatal giant cell hepatitis in a Denver Children’s Series, 27% had NPD type C. Splenomegaly was a useful clue.
In cases of neonatal hepatitis, the relative proportion of inflammatory cells is not considered informative, because ongoing apoptosis may lead to extensive hepatocyte destruction and accumulation of residual lymphocytes and macrophages. In some cases, parenchymal inflammation is minimal or absent. in addition, parenchymal neutrophils are an uncommon finding. Occasional islands of erythropoiesis are a normal finding. In all instances, the biopsy specimen should be examined carefully for evidence of viral cytopathic change.
Portal tracts may be inconspicuous, whether normal or abnormal. In general, at least five to seven portal tracts are required to consider the tissue sample adequate for histologic evaluation. Ten or more portal tracts are preferred. Bile duct hypoplasia was more common among infants with hypopituitarism, compared with other conditions, in the Johns Hopkins/University of Chicago series. No other biopsy finding was helpful in distinguishing possible etiologies in that series. Exclusion of biliary atresia or A1AT storage disorder requires verification that most, if not all, portal tracts contain a terminal bile duct, a companion hepatic artery, and a portal vein and that bile ductular proliferation, edema, neutrophilic inflammation, and fibrosis are absent. Although the portal tracts in patients with neonatal hepatitis may be expanded by a mixed inflammatory infiltrate, this should not be confused with normal granulocytic hematopoiesis occasionally found within portal tracts.
Occasionally, massive hepatic necrosis, with severe accumulation of parenchymal iron, may be observed in patients with Down syndrome. One infant in the Texas Children’s Hospital series had an exceptional degree of hepatocellular necrosis, and the cause was pyruvate kinase deficiency. The observation of massive necrosis should also prompt consideration of neonatal hemochromatosis (discussed earlier; see Table 54.6 ).
Once EHBA and A1AT mutations have been excluded on the basis of both clinical findings and percutaneous liver biopsy, then the differential diagnosis of neonatal hepatitis syndrome must be pursued. Infections of the newborn have been mentioned, and Chapter 46 addresses some of these disorders. Extensive lobular disease, with or without giant cells, may be seen in patients with EHBA (see Fig. 54.4 ). Therefore, lobular changes should not divert attention from the features in the portal tracts. Second, nonclassic features of EHBA, in which intrahepatic bile ducts have yet to proliferate, may be observed in biopsy specimens from patients with biliary atresia (see Fig. 54.5, B ). Sometimes, alert detection of acholic stools prompts an early biopsy, but the time of onset and rate of progression can vary greatly. (For a detailed discussion of the differential diagnosis, see Cholestatic Pattern and Table 54.6 .)
Natural History and Treatment
The natural history of neonatal hepatitis depends heavily on the specific etiology ( Table 54.15 ). For instance, pharmacologic intervention is imperative for many of the infectious disorders. Many of the other disorders, including hypopituitarism, tyrosinemia, and bile salt synthetic defects, benefit dramatically from prompt intervention. In about one quarter of all infants, no cause is found. The prognosis for “idiopathic” neonatal hepatitis syndrome is considered favorable; the mortality rate is 13% to 25%. Predictors of a poor clinical outcome include severe or prolonged (>6 months) jaundice, alcholic stools, familial occurrence, and persistent hepatomegaly. Peak bilirubin level is not predictive of outcome. Sepsis is a devastating complication and is associated with a poor outcome. For infants whose liver disease resolves, the prognosis is quite good; most have no residual liver dysfunction.
|Biliary atresia||Death by 1 to 2 yr of age without Kasai procedure or liver transplantation|
|α 1 -Antitrypsin storage disorder||Progressive chronic liver disease with risk of cirrhosis|
|Neonatal infection||Resolution of infection required for survival|
|Disorders of carbohydrate metabolism|
|Glycogen storage disease||Maintenance of blood sugar levels enables survival |
Risk of chronic renal disease
High probability of hepatic adenomatosis
Liver transplantation is curative in some forms
|Galactosemia||Dietary galactose restriction enables survival |
Neurodevelopmental complications may persist
|Fructosemia||Avoidance of dietary fructose enables survival |
Lifelong risk of metabolic crises on fructose exposure
|Disorders of amino acid metabolism|
|Tyrosinemia||Pharmacologic treatment enables survival |
High lifetime risk of hepatocellular carcinoma
|Disorders of glycolipid and lipid metabolism|
|Niemann-Pick disease types A and C||Type A: fatal outcome of progressive neurologic disease |
Type C: survival into adulthood possible, neurologic compromise may occur
|Hereditary disorders of bile formation|
|Progressive familial intrahepatic cholestasis||Biliary diversion may ameliorate; liver transplantation for cirrhosis; persistent diarrhea in type 1|
|Disorders of bile acid biosynthesis||Dietary treatment with bile acids can ameliorate effects of disease|
|Idiopathic neonatal hepatitis||Highly variable, most likely representing undiscovered genetic abnormalities |
Cholestatic liver disease may persist into later childhood
The management of idiopathic neonatal hepatitis syndrome is supportive and includes adequate nutrition. Dietary measures, such as use of lactose-free, low-protein formulas, may mitigate further liver damage until the results of tests for galactosemia and hereditary tyrosinemia type I become known. Elemental formulas containing medium-chain triglycerides help maintain caloric intake in severely ill patients. Infants with chronic cholestasis require fat-soluble vitamin supplementation. Pruritus associated with chronic cholestasis is difficult to treat in many patients.
Syncytial Giant Cell Hepatitis
In 1991, a putative novel form of hepatitis was first described in patients aged 5 months to 41 years. Clinical features of a severe type of hepatitis required liver transplantation in five patients; five others died of their liver disease. Liver histology revealed replacement of the parenchyma with abundant large syncytial multinucleated (giant) hepatocytes that contained up to 30 nuclei per cell. Electron microscopy revealed intracytoplasmic structures consistent with paramyxovirus nucleocapsids ( Fig. 54.12 ). Injection of liver homogenate from an affected patient into two chimpanzees led to an increase in the titer of paramyxovirus antibodies in one.