Pyoderma gangrenosum

What it means

A deep skin ulcer with a well defined border, which is usually violet or blue. The ulcer edge is often undermined (worn and damaged) and the surrounding skin is erythematous and indurated. The ulcer often starts as a small papule or collection of papules, which break down to form small ulcers with a so called cat's paw appearance. These coalesce and the central area then undergoes necrosis to form a single ulcer.

Pyoderma gangrenosum can occur on any skin surface, but is most commonly seen on the legs. Patients are often systemically unwell with symptoms such as fever, malaise, arthralgia, and myalgia. Lesions are usually painful and the pain can be severe. When the lesions heal the scars are often cribriform. About half of the cases are associated with underlying systemic conditions, such as inflammatory bowel disease, arthritis, and hematological malignancies.

Rare diseases that can present with this4

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category