108. Pyoderma gangrenosum

A disorder of uncertain cause that may appear on any mucocutaneous surface but has a predilection for the lower extremities. Of the four main clinical variants—ulcerative, pustular, bullous, and vegetative—the ulcerative form is the most prevalent. Along with the pustular variant, the ulcerative form is associated most frequently with active inflammatory bowel disease. The bullous and vegetative forms generally occur with myelodysplastic and lymphoproliferative disorders.

The diagnosis is usually made clinically. Serologic, hematologic, and histopathologic findings are nonspecific. Differential diagnosis includes a wide variety of infections as well as insect or spider bites, drug reactions, vasculitis, and the antiphospholipid-antibody syndrome. Corticosteroids are the mainstay of treatment, and often control and sometimes cure the lesion. Acceptable therapeutic alternatives are dapsone, bactrim, clofazimine, and minocycline. Because trauma can intensify the inflammatory process, debridement is contraindicated.