Pyoderma gangrenosum: an update.

Pyoderma gangrenosum (PG) can be differentiated into classic and atypical forms. The classic form is characterized by ulcers and the atypical form by deep erosions with bullous blue-gray margins. Pathergy, the development of cutaneous lesions at sites of trauma, is a common feature of both forms of PG. Approximately 50% of patients who have PG have underlying systemic diseases, most commonly inflammatory bowel disease, myeloproliferative disorders, and various forms of inflammatory arthritis. The diagnosis of PG is one of exclusion. The management of this disorder begins with treatment of any underlying disease and local or systemic glucocorticoids or immunomodulating therapies.