Pyoderma gangrenosum

Last revised by Craig Hacking on 18 Aug 2021

Pyoderma gangrenosum is a rare non-infectious dermatosis characterized by large, painful ulcerated purulent lesions most commonly over the pretibial region. It can be associated with a number of systemic diseases.

It is most common in people aged 20 to 50 years old. It is rarely found in children and the elderly.

The eruption initially appears are a pustule which enlarges and ulcerates with ill-defined undermined borders that are bluish or violaceous in color. The surrounding skin also becomes edematous. Secondary bacterial infection also occurs with the ulcer becoming purulent. The ulcers are typically painful. Most commonly they occur over the pretibial region, however any skin surface can be affected. Rarely mucous membrane and airway involvement can occur.

The exact etiology of pyoderma gangrenosum is unknown however, neutrophil dysfunction and immunological factors are likely involved. Some cases of pyoderma gangrenosum are idiopathic. However, approximately 50% of patients will have an underlying systemic disorder including:

Iatrogenic cases have also been reported following medication use (e.g. propylthiouracil, pegfilgastrim).

Rarely sterile cortical osteolysis in bone underlying the ulcers can be seen.

High dose systemic steroids are often used in severe or progressively expanding disease. Other immunosuppressive therapies (e.g. cyclosporin A, azithoprine, infliximab) may be used in severe refractory cases and for treating an underlying condition if present.

Although patients may initially respond to treatment relapsing pyoderma gangrenosum occurs in many patients. In severe and chronic cases non-responsive to medical treatment amputation of the affected limb is sometimes warranted.

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