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Inflammatory Bowel disease.

result from an abnormal local immune response against the normal flora of the gut, and probably against some self antigens, in genetically susceptible individuals
Crohn disease may affect from esophagus to anus but most often involves the ileum; about half of cases exhibit noncaseating granulomatous
Ulcerative colitis is a nongranulomatous disease limited to the colon
First-degree relatives are 3 to 20 times more likely
Pathogenesis include imbalance between 2 factors

(1) factors that activate the host immune system, such as luminal microbes, dietary antigens, and endogenous inflammatory stimuli; and
(2) host defenses that down-regulate inflammation and maintain the integrity of the mucosa


Genetic Predisposition:

Ulcerative colitis has been associated with HLA-DRB1, whereas
HLA-DR7 and DQ4 alleles are associated with approximately 30% of Crohn disease

Immunologic Factors

predominant class of T-cell response.The inflammatory cytokine TNF may play an important role and TNF antagonist are used in the treatment
neutrophils initially and mononuclear cells later in the course
perinuclear antineutrophil cytoplasmic antibodies, which are present in about 75% of persons with ulcerative colitis

End results:

(1) impaired integrity of the mucosal epithelial barrier, and
(2) loss of surface epithelial cell absorptive function