Which finding is most characteristic of Crohn disease?

• A. Ulcerative, continuous colitis without skip lesions
• B. Transmural inflammation with skip lesions and noncaseating granulomas
• C. Pancolitis with pseudopolyps
• D. Noninflammatory granulomatous lesions only

Answer: (B)

Distinguishing Crohn disease from other inflammatory bowel diseases by how the inflammation behaves is being tested. Crohn disease characteristically shows inflammation that goes through the full thickness of the bowel wall (transmural) and can affect any part of the GI tract, often in a patchy, segmental pattern with normal-looking bowel in between—these patches are skip lesions. When tissue is examined, noncaseating granulomas may be present. This combination explains why Crohn’s can cause fistulas, strictures, and thickened bowel walls, and why the disease can involve the small intestine as well as the colon.

In contrast, ulcerative colitis presents as continuous inflammation that is limited to the colon and affects only the mucosa and submucosa, starting at the rectum and moving proximally, frequently with pseudopolyps developing during healing. The described pattern of transmural involvement with skip lesions and granulomas is, therefore, the finding most characteristic of Crohn disease.