Pyoderma gangrenosum complicating Crohn's disease.

Of the many acknowledged systemic complications of inflammatory bowel disease, arthritis, iritis and erythema nodosum are observed most commonly and considered parts of the natural history. Pyoderma gangrenosum is a more ominous, less common but similarly associated complication that classically occurs in the course of ulcerative colitis. Its rarity in Crohn's disease stimulated the following report.