Secondary CIPO

Approximately half of the cases of CIPO are secondary to a wide array of diseases including neurologic, metabolic/endocrine, paraneoplastic, autoimmune, and infectious diseases, which may impact at any number of levels on the enteric neuromuscular compartment and/or extraenteric organs with consequences on gut function ( Box 1 ) . For example, several neurologic (eg, Parkinson’s disease and Shy-Drager syndrome) and metabolic disorders (eg, diabetes mellitus) can affect the extrinsic (parasympathetic and/or sympathetic) nerve pathways supplying the digestive system. Paraneoplastic syndromes may evoke an inflammatory/immune infiltrate targeting neurons located in both submucosal and myenteric ganglia of the enteric nervous system (ENS); the cellular infiltrate along with circulating antineuronal antibodies are thought to damage the enteric reflexes thereby contributing to paraneoplastic dysmotility (see below). Many different neurotropic viruses may also cause morphologic (ie, inflammatory) or functional changes of the ENS and extrinsic neural pathways supplying the gut and are detectable in a subset of patients with CIPO. Enteric smooth muscle cells can be selectively damaged in patients with myotonic dystrophy or progressive systemic sclerosis, while autoimmune disorders (eg, scleroderma, dermatomyositis and systemic lupus erythematosus), collagenopathies (eg, Ehlers-Danlos), jejunal diverticulosis and radiation enteritis can alter, not only enteric nerves, but also smooth muscle cells (and likely the ICC), resulting in a combined picture of neuro-myopathy. Similar abnormalities to the neuro-ICC-muscular component are presumed to occur in rare cases of celiac disease associated with CIPO, as suggested by the presence of manometric abnormalities. Other diseases such as hypothyroidism, hypoparathyroidism and pheochromocytoma are known causes of CIPO, although the type and degree of enteric neuro-ICC-muscular damage in these disorders is still a matter of investigation. Thus, because of this clinical heterogeneity, a comprehensive diagnostic work-up (see below) should always be performed in patients with CIPO in order to identify any possible underlying diseases and treat them accordingly.

Genetic CIPO

Although most instances of CIPO are sporadic, different genetic forms have been reported.

Genes involved in the pathogenesis of congenital aganglionosis or Hirschsprung’s disease, namely GDNF (glial-cell line derived neurotrophic factor), GFRA1 (GDNF receptor-α ₁ ), EDN3 (endothelin 3), EDNRB (endothelin 3 receptor B), do not appear to play a role in autosomal dominant CIPO. An exception to this is SOX10 , a gene encoding for a transcription factor and RET regulator exerting an important role in neuronal survival and maintenance. Three sporadic patients carrying de novo SOX10 heterozygous mutations showed a clinical phenotype of CIPO combined with some features of Waardenburg-Shah syndrome (ie, pigmentary anomalies and sensorineural deafness). In these patients full-thickness biopsy obtained at laparotomy revealed apparently normal ganglionic cells ruling out the diagnosis of Hirschsprung’s disease. Therefore, in addition to Hirschsprung’s disease, SOX10 abnormalities may contribute to a more diffuse derangement of gut dysmotility, such as CIPO.

Concerning autosomal recessive CIPO, a large Turkish consanguineous family with several members affected by severe dysmotility and recurrent subocclusive episodes, long-segment Barrett’s esophagus and cardiac involvement was originally reported in 2003. Homozygosity mapping has identified the locus on the region 8q23-q24, although the specific gene responsible for this syndromic CIPO is still under investigation in our group. Another known form of recessive CIPO is the mitochondrial neurogastrointestinal encephalopathy (MNGIE). In addition to severe gut dysmotility, patients with MNGIE manifest with cachexia, ptosis, ophthalmoparesis, peripheral neuropathy and exhibit white matter changes (leukoencephalopathy) on magnetic resonance imaging of the brain. This syndrome is caused by mutations in the thymidine phosphorylase gene ( TYMP , also known as endothelial cell growth factor-1, ECGF1 ) or in the polymerase-γ gene ( POLG , a form of MNGIE without leukoencephalopathy). Gut tissue analysis showed that CIPO in patients with MNGIE is related to an underlying enteric myopathy.

Two types of X-linked CIPO related to mutations of filamin A ( FLNA ) and L1 cell adhesion molecule ( L1CAM ) genes, both mapping on chromosome Xq28, have been reported. An FLNA mutation has been identified in a family with X-linked recessive CIPO with signs of central nervous system involvement. In the other 2 families, where a duplication of the FLNA gene has been identified, CIPO was combined with patent ductus arteriosus and giant-platelet thrombocytopenia. A recent histopathologic characterization of gut tissue specimens from five patients with FLNA mutations showed that myopathy, rather than neuropathy, accounts for the severe dysmotility of this familial form of CIPO.

Finally, CIPO has been reported in patients with inherited degenerative smooth muscle and enteric neuronal disorders, termed familial visceral myopathy and neuropathy, respectively, but the underlying genes responsible for both clinical phenotypes have not been identified.

Histopathologic Features and Putative Mechanisms in CIPO

The majority of sporadic cases of CIPO has an undefined etio-pathogenesis. Nonetheless, the potential to collect full-thickness specimens via minimally invasive approaches and advances in the major techniques used to study biopsies (for further details see article by Knowles and Martin elsewhere in this issue) helped to minimize the uncertainty linked to previously labeled “idiopathic” CIPO. Also, a better appraisal of the underlying neuro-ICC-muscular changes associated with CIPO and other gastrointestinal motility disorders has been recently proposed by the Gastro 2009 International Working Group on Gastrointestinal Neuromuscular Disorders (GINMD). Accordingly, CIPO can be due to underlying neuropathies, myopathies and, although at a lower level of evidence, mesenchymopathies, based on neuronal, muscular or ICC involvement, respectively. Nonetheless, it is worth noting that combined abnormalities, eg, neuro-myopathy, neuro-mesenchymopathy or other pictures, are increasingly recognized.

There are 2 main histopathologic pictures of enteric neuropathies, namely inflammatory and degenerative.

Inflammatory (or immune-mediated) neuropathies are characterized by CD3 ⁺ T lymphocytes (and, to a lower extent, plasma cells) infiltrating enteric neurons in the 2 ganglionated plexuses of the ENS (hence the term “enteric ganglionitis”). For still unclear reasons, the inflammatory infiltrate more commonly targets myenteric (ie, “myenteric ganglionitis”) rather than submucosal ganglia. Also, axons giving off the myenteric ganglia and running throughout the muscular layer of the gut can exhibit an inflammatory axonopathy.

Evidence of either enteric or myenteric lymphocytic ganglionitis in small bowel full thickness biopsies has been reported in 33 of 115 and in 17 of 50 patients with CIPO by Knowles and colleagues and Lindberg and colleagues, respectively. Usually, the definition of lymphocytic ganglionitis is easily applicable when an overt infiltration of lymphocytes can be detected within myenteric ganglia. However, a low-grade myenteric ganglionitis, characterized by a less prominent inflammatory cell infiltration, has been demonstrated in most CIPO and other forms of severe dysmotility. Thus, a quantitative evaluation of the number of lymphocytes may be necessary for an appropriate diagnosis of an underlying inflammatory neuropathy. Although there are no normative data on the number of lymphocytes within myenteric ganglia in healthy controls, it has been proposed by the Gastro 2009 International Working Group on GINMD that 5 or more lymphocytes per ganglion would be enough to indicate the presence of a myenteric ganglionitis. Thus, Lindberg and colleagues found a low-grade ganglionitis in 59 patients with dysmotility (one-third of these had CIPO) and the mean number of lymphocytes/ganglion was 5.1. Further research on lymphocytic ganglionitis will be necessary to establish the criteria for appropriate definition of this entity and actual pathogenetic relevance in CIPO. Lymphocytic myenteric ganglionitis may be associated with neuronal changes indicative of degeneration and loss up to complete ganglion cell depletion occurring in the most severe cases.

Patients with lymphocytic myenteric ganglionitis may develop a humoral response characterized by antinuclear neuronal antibodies (ANNA-1 or, based on their molecular target, also referred to as anti-Hu). These autoantibodies alter ascending reflex pathway of peristalsis in in vitro preparations, elicit neuronal hyperexcitability, evoke apoptotic and autophagic mechanisms in primary culture of myenteric neurons or neuronal cell lines. Taken together, the lymphocytic infiltrate in myenteric ganglia and anti-neuronal autoantibodies can exert a pathogenetic role in patients with CIPO related to an inflammatory neuropathy.

Other types of inflammatory neuropathies reported in CIPO are characterized by either eosinophils or mast cells infiltrating and/or surrounding myenteric ganglia. Given the limited number of patients so far reported, the clinicopathologic features of these peculiar forms of nonlymphocytic ganglionitis remain largely unclear.

Compared to inflammatory neuropathies, degenerative (noninflammatory) neuropathies are less well understood. Histopathologic findings may include a number of changes, ie, reduction of intramural (mainly myenteric) neurons associated with swollen cell bodies and processes, fragmentation and loss of axons. Similar to neurodegenerative disorders of the central nervous system, mechanisms such as altered calcium signaling, mitochondrial dysfunction, and production of free radicals are thought to contribute to enteric neurodegeneration and loss. Accordingly, apoptosis may also occur in the ENS of CIPO patients. Few studies have accurately documented the prevalence of degenerative neuropathy in CIPO. In our experience, ENS abnormalities characterized by frank degeneration were detected in 10 of 11 CIPO patients who had available histopathology. Finally, glial cells, which exerts a key role in ENS maintenance and survival, can exhibit abnormalities (now referred to as gliopathy), which can account for enteric neuronal degeneration. Although plausible, the existence of a gliopathy in CIPO needs to be confirmed.

As for neuropathies, enteric myopathies can also be categorized into inflammatory and degenerative forms. Inflammatory myopathies, also referred to as leiomyositis, are characterized by an immune infiltrate, mainly composed by CD4 ⁺ and CD8 ⁺ lymphocytes; thus they can be considered the muscular counterpart of inflammatory neuropathies. Adult cases of leyomiositis with an associated clinical picture of severe CIPO have been reported. If not arrested by immunosuppressive therapy (see later), the progression of leiomyositis may be life-threatening as it evolves toward major disruption of both circular and longitudinal muscle coats throughout the gut.

Regarding degenerative myopathies, both familial and sporadic forms have been recognized. The histopathologic features do not permit differentiation between sporadic and familial myopathies as smooth muscle cell vacuolization and fibrosis can be detected in both. Familial visceral myopathy (FVM, also referred to as “hollow visceral myopathy”) encompasses at least 2 phenotypes, namely type I and II. FVM type I is autosomal dominant and associated with gastrointestinal (megaesophagus, megaduodenum) and extragastrointestinal (megacystis, mydriasis) manifestations. FVM type II is autosomal recessive and corresponds to MNGIE. Vacuolization and fibrosis are mainly localized to the longitudinal, rather than circular, muscle layer of the small bowel with the resultant formation of diverticula. In sporadic degenerative myopathy, smooth muscle vacuolization and fibrosis affect both circular and longitudinal layers of the intestinal wall. The prevalence of myopathy in CIPO has been shown to be quite low in most reported series, with the exception of one study by Mann and colleagues who found more myopathic than neuropathic CIPO. None of our 11 cases of CIPO had signs indicative of smooth muscle damage. In order to improve the diagnostic yield of gut muscle pathology, Wedel and colleagues investigated different specimens from patients with severe dysmotility, including slow transit constipation, idiopathic megacolon, Hirschsprung’s disease, but not cases of CIPO, using immunohistochemical analysis with a panel of different smooth muscle markers (ie, smooth muscle myosin heavy chain [SMMHC], smoothelin [SM] and histone deacetylase 8 [HDAC8]). Compared to classic histochemical techniques (H&E, Masson’s trichrome) and smooth muscle alpha-actin (alpha-SMA) immunolabeling, which turned out to be normal, the expression of SMMHC, SM and HDAC8 was either absent or focally lacking in Hirschsprung’s disease (80%), idiopathic megacolon (75%) and slow-transit constipation (70%). These findings, which have been confirmed by ultrastructural evaluation, indicate subtle (ie, molecular) changes otherwise undetectable with routine stains or alpha-SMA immunohistochemistry. Similar changes to SMMHC, SM and HDAC8 immunolabeling may be expected to occur in CIPO, but supportive data are needed.

ICC network abnormalities (also labeled as mesenchymopathies) have been detected in patients with CIPO. In our hands, decreased ICC density, loss of processes and damaged intracellular cytoskeleton and organelles, as revealed by c-Kit immunohistochemistry have been detected in 5/11 CIPO patients. Given the significant physiologic role exerted by ICCs in gut motility, it has been proposed that their impairment may contribute to the enteric dysmotility leading to CIPO. Nonetheless, the International Working Group on gastrointestinal neuromuscular pathology considered it as yet premature to attribute an etiologic role to ICC changes in several gut motility disorders, with the exception of diabetic gastroparesis.

Secondary CIPO

Approximately half of the cases of CIPO are secondary to a wide array of diseases including neurologic, metabolic/endocrine, paraneoplastic, autoimmune, and infectious diseases, which may impact at any number of levels on the enteric neuromuscular compartment and/or extraenteric organs with consequences on gut function ( Box 1 ) . For example, several neurologic (eg, Parkinson’s disease and Shy-Drager syndrome) and metabolic disorders (eg, diabetes mellitus) can affect the extrinsic (parasympathetic and/or sympathetic) nerve pathways supplying the digestive system. Paraneoplastic syndromes may evoke an inflammatory/immune infiltrate targeting neurons located in both submucosal and myenteric ganglia of the enteric nervous system (ENS); the cellular infiltrate along with circulating antineuronal antibodies are thought to damage the enteric reflexes thereby contributing to paraneoplastic dysmotility (see below). Many different neurotropic viruses may also cause morphologic (ie, inflammatory) or functional changes of the ENS and extrinsic neural pathways supplying the gut and are detectable in a subset of patients with CIPO. Enteric smooth muscle cells can be selectively damaged in patients with myotonic dystrophy or progressive systemic sclerosis, while autoimmune disorders (eg, scleroderma, dermatomyositis and systemic lupus erythematosus), collagenopathies (eg, Ehlers-Danlos), jejunal diverticulosis and radiation enteritis can alter, not only enteric nerves, but also smooth muscle cells (and likely the ICC), resulting in a combined picture of neuro-myopathy. Similar abnormalities to the neuro-ICC-muscular component are presumed to occur in rare cases of celiac disease associated with CIPO, as suggested by the presence of manometric abnormalities. Other diseases such as hypothyroidism, hypoparathyroidism and pheochromocytoma are known causes of CIPO, although the type and degree of enteric neuro-ICC-muscular damage in these disorders is still a matter of investigation. Thus, because of this clinical heterogeneity, a comprehensive diagnostic work-up (see below) should always be performed in patients with CIPO in order to identify any possible underlying diseases and treat them accordingly.

Genetic CIPO

Although most instances of CIPO are sporadic, different genetic forms have been reported.

Genes involved in the pathogenesis of congenital aganglionosis or Hirschsprung’s disease, namely GDNF (glial-cell line derived neurotrophic factor), GFRA1 (GDNF receptor-α ₁ ), EDN3 (endothelin 3), EDNRB (endothelin 3 receptor B), do not appear to play a role in autosomal dominant CIPO. An exception to this is SOX10 , a gene encoding for a transcription factor and RET regulator exerting an important role in neuronal survival and maintenance. Three sporadic patients carrying de novo SOX10 heterozygous mutations showed a clinical phenotype of CIPO combined with some features of Waardenburg-Shah syndrome (ie, pigmentary anomalies and sensorineural deafness). In these patients full-thickness biopsy obtained at laparotomy revealed apparently normal ganglionic cells ruling out the diagnosis of Hirschsprung’s disease. Therefore, in addition to Hirschsprung’s disease, SOX10 abnormalities may contribute to a more diffuse derangement of gut dysmotility, such as CIPO.

Concerning autosomal recessive CIPO, a large Turkish consanguineous family with several members affected by severe dysmotility and recurrent subocclusive episodes, long-segment Barrett’s esophagus and cardiac involvement was originally reported in 2003. Homozygosity mapping has identified the locus on the region 8q23-q24, although the specific gene responsible for this syndromic CIPO is still under investigation in our group. Another known form of recessive CIPO is the mitochondrial neurogastrointestinal encephalopathy (MNGIE). In addition to severe gut dysmotility, patients with MNGIE manifest with cachexia, ptosis, ophthalmoparesis, peripheral neuropathy and exhibit white matter changes (leukoencephalopathy) on magnetic resonance imaging of the brain. This syndrome is caused by mutations in the thymidine phosphorylase gene ( TYMP , also known as endothelial cell growth factor-1, ECGF1 ) or in the polymerase-γ gene ( POLG , a form of MNGIE without leukoencephalopathy). Gut tissue analysis showed that CIPO in patients with MNGIE is related to an underlying enteric myopathy.

Two types of X-linked CIPO related to mutations of filamin A ( FLNA ) and L1 cell adhesion molecule ( L1CAM ) genes, both mapping on chromosome Xq28, have been reported. An FLNA mutation has been identified in a family with X-linked recessive CIPO with signs of central nervous system involvement. In the other 2 families, where a duplication of the FLNA gene has been identified, CIPO was combined with patent ductus arteriosus and giant-platelet thrombocytopenia. A recent histopathologic characterization of gut tissue specimens from five patients with FLNA mutations showed that myopathy, rather than neuropathy, accounts for the severe dysmotility of this familial form of CIPO.

Finally, CIPO has been reported in patients with inherited degenerative smooth muscle and enteric neuronal disorders, termed familial visceral myopathy and neuropathy, respectively, but the underlying genes responsible for both clinical phenotypes have not been identified.

Histopathologic Features and Putative Mechanisms in CIPO

The majority of sporadic cases of CIPO has an undefined etio-pathogenesis. Nonetheless, the potential to collect full-thickness specimens via minimally invasive approaches and advances in the major techniques used to study biopsies (for further details see article by Knowles and Martin elsewhere in this issue) helped to minimize the uncertainty linked to previously labeled “idiopathic” CIPO. Also, a better appraisal of the underlying neuro-ICC-muscular changes associated with CIPO and other gastrointestinal motility disorders has been recently proposed by the Gastro 2009 International Working Group on Gastrointestinal Neuromuscular Disorders (GINMD). Accordingly, CIPO can be due to underlying neuropathies, myopathies and, although at a lower level of evidence, mesenchymopathies, based on neuronal, muscular or ICC involvement, respectively. Nonetheless, it is worth noting that combined abnormalities, eg, neuro-myopathy, neuro-mesenchymopathy or other pictures, are increasingly recognized.

There are 2 main histopathologic pictures of enteric neuropathies, namely inflammatory and degenerative.

Inflammatory (or immune-mediated) neuropathies are characterized by CD3 ⁺ T lymphocytes (and, to a lower extent, plasma cells) infiltrating enteric neurons in the 2 ganglionated plexuses of the ENS (hence the term “enteric ganglionitis”). For still unclear reasons, the inflammatory infiltrate more commonly targets myenteric (ie, “myenteric ganglionitis”) rather than submucosal ganglia. Also, axons giving off the myenteric ganglia and running throughout the muscular layer of the gut can exhibit an inflammatory axonopathy.

Evidence of either enteric or myenteric lymphocytic ganglionitis in small bowel full thickness biopsies has been reported in 33 of 115 and in 17 of 50 patients with CIPO by Knowles and colleagues and Lindberg and colleagues, respectively. Usually, the definition of lymphocytic ganglionitis is easily applicable when an overt infiltration of lymphocytes can be detected within myenteric ganglia. However, a low-grade myenteric ganglionitis, characterized by a less prominent inflammatory cell infiltration, has been demonstrated in most CIPO and other forms of severe dysmotility. Thus, a quantitative evaluation of the number of lymphocytes may be necessary for an appropriate diagnosis of an underlying inflammatory neuropathy. Although there are no normative data on the number of lymphocytes within myenteric ganglia in healthy controls, it has been proposed by the Gastro 2009 International Working Group on GINMD that 5 or more lymphocytes per ganglion would be enough to indicate the presence of a myenteric ganglionitis. Thus, Lindberg and colleagues found a low-grade ganglionitis in 59 patients with dysmotility (one-third of these had CIPO) and the mean number of lymphocytes/ganglion was 5.1. Further research on lymphocytic ganglionitis will be necessary to establish the criteria for appropriate definition of this entity and actual pathogenetic relevance in CIPO. Lymphocytic myenteric ganglionitis may be associated with neuronal changes indicative of degeneration and loss up to complete ganglion cell depletion occurring in the most severe cases.

Patients with lymphocytic myenteric ganglionitis may develop a humoral response characterized by antinuclear neuronal antibodies (ANNA-1 or, based on their molecular target, also referred to as anti-Hu). These autoantibodies alter ascending reflex pathway of peristalsis in in vitro preparations, elicit neuronal hyperexcitability, evoke apoptotic and autophagic mechanisms in primary culture of myenteric neurons or neuronal cell lines. Taken together, the lymphocytic infiltrate in myenteric ganglia and anti-neuronal autoantibodies can exert a pathogenetic role in patients with CIPO related to an inflammatory neuropathy.

Other types of inflammatory neuropathies reported in CIPO are characterized by either eosinophils or mast cells infiltrating and/or surrounding myenteric ganglia. Given the limited number of patients so far reported, the clinicopathologic features of these peculiar forms of nonlymphocytic ganglionitis remain largely unclear.

Compared to inflammatory neuropathies, degenerative (noninflammatory) neuropathies are less well understood. Histopathologic findings may include a number of changes, ie, reduction of intramural (mainly myenteric) neurons associated with swollen cell bodies and processes, fragmentation and loss of axons. Similar to neurodegenerative disorders of the central nervous system, mechanisms such as altered calcium signaling, mitochondrial dysfunction, and production of free radicals are thought to contribute to enteric neurodegeneration and loss. Accordingly, apoptosis may also occur in the ENS of CIPO patients. Few studies have accurately documented the prevalence of degenerative neuropathy in CIPO. In our experience, ENS abnormalities characterized by frank degeneration were detected in 10 of 11 CIPO patients who had available histopathology. Finally, glial cells, which exerts a key role in ENS maintenance and survival, can exhibit abnormalities (now referred to as gliopathy), which can account for enteric neuronal degeneration. Although plausible, the existence of a gliopathy in CIPO needs to be confirmed.

As for neuropathies, enteric myopathies can also be categorized into inflammatory and degenerative forms. Inflammatory myopathies, also referred to as leiomyositis, are characterized by an immune infiltrate, mainly composed by CD4 ⁺ and CD8 ⁺ lymphocytes; thus they can be considered the muscular counterpart of inflammatory neuropathies. Adult cases of leyomiositis with an associated clinical picture of severe CIPO have been reported. If not arrested by immunosuppressive therapy (see later), the progression of leiomyositis may be life-threatening as it evolves toward major disruption of both circular and longitudinal muscle coats throughout the gut.

Regarding degenerative myopathies, both familial and sporadic forms have been recognized. The histopathologic features do not permit differentiation between sporadic and familial myopathies as smooth muscle cell vacuolization and fibrosis can be detected in both. Familial visceral myopathy (FVM, also referred to as “hollow visceral myopathy”) encompasses at least 2 phenotypes, namely type I and II. FVM type I is autosomal dominant and associated with gastrointestinal (megaesophagus, megaduodenum) and extragastrointestinal (megacystis, mydriasis) manifestations. FVM type II is autosomal recessive and corresponds to MNGIE. Vacuolization and fibrosis are mainly localized to the longitudinal, rather than circular, muscle layer of the small bowel with the resultant formation of diverticula. In sporadic degenerative myopathy, smooth muscle vacuolization and fibrosis affect both circular and longitudinal layers of the intestinal wall. The prevalence of myopathy in CIPO has been shown to be quite low in most reported series, with the exception of one study by Mann and colleagues who found more myopathic than neuropathic CIPO. None of our 11 cases of CIPO had signs indicative of smooth muscle damage. In order to improve the diagnostic yield of gut muscle pathology, Wedel and colleagues investigated different specimens from patients with severe dysmotility, including slow transit constipation, idiopathic megacolon, Hirschsprung’s disease, but not cases of CIPO, using immunohistochemical analysis with a panel of different smooth muscle markers (ie, smooth muscle myosin heavy chain [SMMHC], smoothelin [SM] and histone deacetylase 8 [HDAC8]). Compared to classic histochemical techniques (H&E, Masson’s trichrome) and smooth muscle alpha-actin (alpha-SMA) immunolabeling, which turned out to be normal, the expression of SMMHC, SM and HDAC8 was either absent or focally lacking in Hirschsprung’s disease (80%), idiopathic megacolon (75%) and slow-transit constipation (70%). These findings, which have been confirmed by ultrastructural evaluation, indicate subtle (ie, molecular) changes otherwise undetectable with routine stains or alpha-SMA immunohistochemistry. Similar changes to SMMHC, SM and HDAC8 immunolabeling may be expected to occur in CIPO, but supportive data are needed.

ICC network abnormalities (also labeled as mesenchymopathies) have been detected in patients with CIPO. In our hands, decreased ICC density, loss of processes and damaged intracellular cytoskeleton and organelles, as revealed by c-Kit immunohistochemistry have been detected in 5/11 CIPO patients. Given the significant physiologic role exerted by ICCs in gut motility, it has been proposed that their impairment may contribute to the enteric dysmotility leading to CIPO. Nonetheless, the International Working Group on gastrointestinal neuromuscular pathology considered it as yet premature to attribute an etiologic role to ICC changes in several gut motility disorders, with the exception of diabetic gastroparesis.