Pyoderma gangrenosum.

Pyoderma gangrenosum (PG) is an idiopathic, painful and destructive condition that usually presents as an ulceration on the pretibial region of the legs. It primarily affects patients with inflammatory bowel disease, arthritis, myeloproliferative disorders and chronic hepatitis, and occasionally affects patients with other conditions, but it may also occur without any associated illness. Since there are no specific serologic or histologic markers for PG, it must be diagnosed clinically. Treatment usually involves immunosuppressant therapy as well as treatment of the underlying disease. The course of PG is unpredictable, and prognosis depends on the extent of the skin lesions at the time of diagnosis, underscoring the need for early and aggressive management.