Crohn Disease

Epidemiology:

Common sites:

Gross features:

• creeping fat
• rubbery, thick intestinal wall
• narrowed lumen
• aphthous ulcers are early lesions
• serpentine linear longitudinal ulcers

Histologic features:

• Major diagnostic features suggestive of Crohn’s disease:
• Granulomas
• Significant ileal involvement
• Transmural lymphoid aggregates
• Fistula tract formation
• focal involvement within and between biopsies is the hallmark of Crohn’s
• 3 important and easy diagnostic features for IBD:
• architectural distortion (variation from orderly test-tubes, branching, budding)
• thickened, reduplicated MM is an indication of previous ulceration
• deep plasma cells within chronic inflammatory infiltrate – lower 2/3rds of lamina propria
• note that deep plasma cells are normal in the cecum and terminal ileum
• Paneth cell metaplasia – shouldn’t see Paneth cells past hepatic flexure
• Ulceration – superficial or deep
• If beyond muscularis propria, it is Crohn rather than UC
• Prominent lymphoid aggregates
• Should consist of only lymphocytes
• “rosary bead” pattern subserosally
• more specific for CD if transmural and away from areas of ulceration
• Granulomas (sarcoid-like)
• Note that granulomas may be normal near ruptured crypts
• May be present at all layers of bowel wall
• May be present in uninvolved areas as well as active areas
• Eosinophils stick around between attacks

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

Other features:

References: