Crohn Disease
Differential Diagnosis
- Fungal, mycobacterial, amebic and other parasitic diseases must all be ruled out by close inspection and by laboratory tests
- Necrotic granulomas strongly suggest infection
- In cases of colitis refractory to treatment, cytomegalovirus must be ruled out immunohistochemically
- Quiescent colitis may be histologically indistinguishable from the effects of radiation or chemotherapy or chronic ischemia
- Clinical correlation is necessary
- Segmental colitis associated with sigmoid diverticular disease may be histologically identical to Crohn disease
- Clinical correlation is necessary
| Ulcerative Colitis | Crohn Disease |
| Inflammation limited to mucosa and superficial submucosa | Transmural inflammation |
| Contiguous disease, no skip lesions | Discontinuous, patchy disease with skip lesions |
| Limited to colon | May involve entire GI tract |
| No granulomas | Granulomas may be present |
| Predominantly neutrophilic infiltrate with crypt abscesses | Predominantly lympho-histiocytic infiltrate |
| Perinuclear anti-neutrophilic cytoplasmic antibody (pANCA) favors ulcerative colitis | Anti-Saccharomyces cerevisiae antibody (ASCA) favors Crohn disease |
- The distinction may be impossible on biopsies and always requires clinical correlation
- Rare cases deviate from some of these criteria
- Up to 15% of cases may be indeterminate even after full evaluation
- pANCA and ASCA have considerable overlap and are felt by some to lack clinical utility
| Mucosal Prolapse / Cloacogenic Polyp (Solitary Rectal Ulcer) | Crohn Disease |
| Shallow ulceration | Deep ulcers and fissures |
| Restricted to rectum (rarely in sigmoid) | May involve any part of GI tract |
| Not concentric, usually localized to anterior rectal wall | Usually concentric |
| Frequently forms a polyp that appears hamartomatous with muscularis mucosae extension into lamina propria | No polyp formation or muscularis mucosae extension into lamina propria |
| Crohn Disease | Common Variable Immunodeficiency – GI Involvement |
| Skip lesions predominate | Usually diffuse |
| Transmural inflammation | Mild lamina propria infiltrate with nodular lymphoid hyperplasia |
| Numerous plasma cells | Plasma cells frequently markedly decreased |
| Deep fissures frequent | No fissures or deep ulcers |
| Incidental Chronic Colitis | Crohn Disease |
| Isolated disease | Usually multifocal |
| Virtually restricted to cecum/right colon | May involve entire GI tract |
| No granulomas | Granulomas may be present |
| Incidental, asymptomatic | Nearly always symptomatic |
- Histologically indistinguishable
