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Pyoderma gangrenosum: Pathogenesis, clinical features, and diagnosis

Courtney Schadt, MD
Section Editor
Jeffrey Callen, MD, FACP, FAAD
Deputy Editor
Abena O Ofori, MD


Pyoderma gangrenosum (PG) is an uncommon neutrophilic dermatosis that presents as an inflammatory and ulcerative disorder of the skin. In contrast to its name, PG is neither an infectious nor gangrenous condition. The most common presentation of PG is an inflammatory papule or pustule that progresses to a painful ulcer with a violaceous undermined border and a purulent base (picture 1A-E). PG may also present with bullous, vegetative, peristomal, and extracutaneous lesions.

More than half of patients with PG develop the disorder in association with an underlying systemic disease. Inflammatory bowel disease, hematologic disorders, and arthritis represent the most frequent comorbidities.

A diagnosis of PG rests upon the recognition of consistent clinical and histologic findings and the exclusion of other inflammatory or ulcerative cutaneous disorders. There are no pathognomonic clinical or histological findings of PG.

The pathogenesis, clinical manifestations, and diagnosis of PG will be discussed here. The treatment and prognosis of PG and other neutrophilic dermatoses are reviewed separately. (See "Pyoderma gangrenosum: Treatment and prognosis" and "Neutrophilic dermatoses".)


PG is a rare disorder with an estimated incidence of 3 to 10 cases per million people per year [1]. Individuals of any age may be affected, including children [2-4]. PG most commonly develops in young and middle aged adults, with an average age of onset between 40 and 60 years [5-8]. Between the sexes, women are more frequently affected [7].


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Literature review current through: Sep 2016. | This topic last updated: Oct 14, 2016.
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