What is it?

Pyoderma gangrenosum is an inflammatory skin disorder presenting with ulcers.

What causes it?

The exact cause of pyoderma gangrenosum is not known. However, around half of cases are seen in association with systemic conditions, most commonly inflammatory bowel disease (Crohn disease and ulcerative colitis).  Lesions are triggered by local trauma, which is known as pathergy.

What does it look like?

Pyoderma gangrenosum often starts at a site of minor injury such as a cut or scrape. It begins as a pustule which eventually ulcerates and is very painful. The ulcers of pyoderma gangrenosum have a classic appearance with a well-defined border with a rolled, deep-purple rim. It resolves with characteristic cribriform scarring (a lattice-like pattern).

How is it diagnosed?

Pyoderma gangrenosum is a diagnosis of exclusion. Other causes of ulcers such as infections, venous/arterial insufficiency, vasculitis, panniculitis, pressure sores and malignancy should be ruled out, which may require wound swabs and/or biopsy.

How is it managed?

Aggressive debridement should be avoided as this can trigger new ulcers to form. Smaller lesions can be treated with topical or intralesional corticosteroids and wound care. More severe cases may require systemic anti-inflammatory agents such as corticosteroids, cyclosporine or anti-TNF biologics.