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| Fig. 37.2 Pyoderma gangrenosum. Large necrotic undermined ulcer of the lower leg with exposed tendon in a patient with ulcerative colitis. (Courtesy of the Fitzsimons Army Medical Center teaching files.) |
Pyoderma gangrenosum (PG) is a severe ulcerative condition that affects 1 in 100,000 United States citizens per year and, in over 70% of cases, affects the lower legs (Fig. 37-2). It is one of the skin lesions associated with the abdominal pain and bleeding of inflammatory bowel disease. PG originates as a small, tender pustule that breaks down to form a painful, rapidly expanding necrotic ulcer with a cyanotic, raised and undermined edge. Lesions may develop at sites of minor trauma, a phenomenon known as pathergy. The ulcers of PG may become quite large. They frequently heal with a thin, atrophic scar.
The exact cause of PG is unknown, but immune complex–mediated neutrophilic vascular reactions in the skin have been postulated. After the diagnosis of PG is made, the next step should be to look for an underlying cause. Important conditions to search for include chronic infectious hepatitis, inflammatory bowel disease (ulcerative colitis or Crohn’s disease), rheumatoid arthritis, lupus erythematosus, HIV infection, and leukemia. About 2% of patients with ulcerative colitis have PG, and the course of both illnesses maybe parallel. Some patients may have PG for several years before developing inflammatory bowel disease. In general, firstline treatment is corticosteroids and cyclosporine. Infliximab (TNF-α antibody) is the treatment of choice for PG with underlying inflammatory bowel disease or rheumatoid arthritis.
Brooklyn T, Dunnill G, Probert C: Diagnosis and treatment of pyoderma gangrenosum,
BMJ 333(7560):181–184, 2006.
