Pyoderma gangrenosum
Pyoderma gangrenosum is a rare neutrophilic ulcerative disease that begins as a tender pustule or nodule and rapidly evolves into a painful ulcer with a violaceous, undermined border, most often in patients with inflammatory bowel disease, inflammatory arthritis, or a hematologic disorder. Diagnosis is clinical and by exclusion after biopsy and culture; first-line treatment is systemic glucocorticoids or cyclosporine, and debridement must be avoided because of pathergy.
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What this article covers
- Overview
Definition: pyoderma gangrenosum (PG) is a rare, painful ulcerative neutrophilic disease of the skin of unknown origin, classified alongside Sweet syndrome as a neutrophilic dermatosis.
- Epidemiology
Rarity: the estimated prevalence in the United States is 5.8 patients per 100,000 adults.
- Risk factors
Inflammatory bowel disease: the single most common systemic association, with skin lesions occurring in roughly 10% of patients with inflammatory bowel disease as one of erythema nodosum, pyoderma gangrenosum, or aphthous ulcers.
- Pathophysiology
Neutrophilic infiltrate: histopathology classically shows a pandermal infiltrate predominantly composed of neutrophils with associated dermal edema, without evidence of true vasculitis or infection.
- Clinical features
Diagnostic lesion morphology: a tender nodule or pustule rapidly progresses to a painful ulcer with a ragged, undermined, violaceous or gunmetal-colored border and a purulent, exudative base…
- Differential diagnosis
Venous ulcer: typically at the medial malleolus, shallow and irregular with weeping exudate and variable pain that improves with leg elevation, unlike the exquisitely painful, violaceous, undermined border of pyoderma gangrenosum.
- Diagnosis
Diagnostic basis: pyoderma gangrenosum is a clinical diagnosis of exclusion, established by the characteristic painful ulcer with a violaceous, undermined border after infection and malignancy have…
- Management
First step for every active lesion: do not debride the ulcer; sharp debridement of devitalized tissue helps most other ulcers but worsens pyoderma gangrenosum through pathergy.
- Complications
Deep tissue exposure: rapidly enlarging ulcers can expose underlying tendon or muscle, particularly when the diagnosis is missed and inappropriate debridement worsens the wound.
- Prognosis
Course tracks the associated disease loosely: in inflammatory bowel disease, PG typically follows an independent course from bowel disease activity, so colitis control alone does not guarantee skin improvement.
- Prevention
Avoid elective trauma to skin in patients with known pyoderma gangrenosum, including unnecessary surgery, biopsies, or piercings, given the 20 to 30% risk of pathergy-induced new lesions.
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- Lower extremity ulcers
Lower extremity ulcers are open skin breaks below the knee that fall into three clinically distinct patterns, venous stasis, arterial insufficiency, and diabetic neuropathic, distinguished chiefly by location, pain, and behavior with leg position, plus the pyoderma gangrenosum exception that must not be debrided. Management is cause-specific: compression and elevation for venous ulcers after confirming an ankle-brachial index above 0.9, revascularization and risk-factor control for arterial ulcers, and offloading with diabetes control for neuropathic ulcers.
- Erythema nodosum
Erythema nodosum is a delayed hypersensitivity panniculitis presenting as symmetric, tender, erythematous subcutaneous nodules on the anterior shins, most commonly following streptococcal pharyngitis but also linked to sarcoidosis, inflammatory bowel disease, Coccidioides, Yersinia, pregnancy, and drugs such as oral contraceptives. Diagnosis is clinical, and management is directed at the underlying cause with NSAIDs, bed rest, and cool compresses for symptom control.