Pyoderma gangrenosum is a cutaneous disorder characterized by slowly progressive ulceration which is refractory to local wound care and antibiotic therapy. The diagnosis is made after the exclusion of other causes of cutaneous ulceration. The cause of pyoderma is thought to be a deficiency in host immune reactivity, and a systemic illness is present in 80% of patients. High-dose corticosteroids and appropriate treatment of the underlying disease represent the mainstays of therapy, although hyperbaric oxygen has recently shown promise in the healing of skin grafts over these lesions.

Rand, Brown, Bostwick, , , , , , (1988). Pyoderma gangrenosum and progressive cutaneous ulceration. Annals of plastic surgery, 1988 Mar;20(3):280-4. https://www.ncbi.nlm.nih.gov/pubmed/2451893