Idiopathic or nonspecific transmural inflammation of the any segment of the GI tract with skip areas of ulceration (aphthous or serpiginous)

In 5-10% of patients with chronic colitis a clear distinction between UC and CD cannot be made even with mucosal biopsy (“indeterminate colitis”)

Infectious: bacterial (E. coli, Salmonella, Shigella, Yersina, Campylobacter, Mycobacterium, C. difficile), amebic, CMV/HSV, STDs

Ischemic colitis, Diverticulitis, Colorectal cancer

Intestinal lymphoma, Collagenous/Lymphocytic colitis (Microscopic colitis), Celiac sprue, Radiation enteropathy

IBS, Appendicitis, Solitary rectal ulcer syndrome

Drugs (NSAID enteropathy, OCP, allopurinol)

Prevalence 1:3000 (high because often presents in younger population initially); ♂ = ♀

Bimodal with peaks in 20’s and 50-70’s; ↑ incidence in Caucasians, Jews, and smokers

The cause is unknown; one theory is cow’s milk containing Mycobacteria Tuberculosis

Mutation of the NOD2/CARD 15 gene found in 20% of patients and is associated with ileal and fibrostenosing disease

Three genetic syndromes associated: Turner’s , Glycogen storage disease 1B, Hermansky-Pudlak (albinism, platelet defect)

Extent: can affect any portion of GI tract from mouth to anus, with skip lesions

Appearance: non-friable mucosa, cobblestoning, deep & long fissures

Microscopy: transmural inflammation with mononuclear cell infiltrate, non-caseating granulomas (Only seen in 10-30% of biopsies), fissures

Smoldering disease with abdominal pain (RLQ) ± abdominal mass; Mucus-containing non-grossly bloody diarrhea

Fevers, malaise, weight loss/malnutrition

Perianal disease: fissures, fistulas

Crohn’s Disease Activity Index (CDAI): used in clinical trials; weighted score of clinical/laboratory values: <150 = Remission, >450 = Severe disease