Characteristic feature of Crohn's disease is?

Ans. is 'a' i.e., Skip lesions * A classic feature of CD is the sharp demarcation of diseased bowel segments from adjacent uninvolved bowelWhen multiple bowel segments are involved, the intervening bowel is normal - skip lesions.Crohn disease (Terminal ileitis or regional enteritis)* Any portion of intestine can be involved, but most commonly small intestine (especially distal ileum) is involved (in 40% cases). Both small intestine and colon are involved in 30% of cases, and only colon isinvolved in 30%.* In the affected segment, mesentric fat wraps around the bowel surface - creeping fat.* The intestinal wall is rubbery and thick, as a consequence of edema, inflammation, fibrosis, and hypertrophy of the muscularis propria - lumen is almost always narrowed - string sign on barium meal.* There are serpentine linear ulcer along the axis of bowel.* As the intervening mucosa tends to be relatively spared, the mucosa acquires a coarse texture - Cobblestone appearance.* Narrow fissures develop between the folds of the mucosa. Fissures can penetrate deeply through the bowel wall and leading to bowel adhesions and serositis. Further extension of fissures leads to fistula or sinus tract formation.* There is transmural inflammation affecting all layers of bowel wall.* Sarcoid like noncaseating granulomas may be present in all tissue layers.* Neutrophilic infiltration into the crypts results in formation of crypt abscess.* Fibrosis of the submucosa, muscularis propria, and mucosa eventually leads to stricture formation.* There is an increased incidence of cancer of GIT in patients with long-standing CD, but the risk of cancer in CD is considerably less than in patients with chronic UC.* On barium enema there is Hose pipe (lead pipe) appearnace and cobble - stone appearnace.* Screening test is presence of anti-Saccharomyces cerevisae antibody (ASCA). Antibody formation is common against cell wall of yeast, Saccharomyces cerevisae in patients of CD.* Extraintestinal manifestations of Crohn disease are skin manifestations (erythema nodosum), migratory polyarthritis, ankylosing spondylitis, sacroilitis, uveitis, clubbing, Hepatic pericholangitis and primary biliary cirrhosis.