DermatologyTier 1Disease (DEADMAN)

Skin ulcers - pyoderma gangrenosum

Description

Rare neutrophilic dermatosis - painful, rapidly progressive ulcer with a violaceous, undermined border
Classic sites: lower legs, but can occur anywhere including peristomal skin

Epidemiology

Uncommon; peak incidence 20-50 years; F>M slightly
~50% associated with an underlying systemic disease

Aetiopathogenesis

Neutrophilic dysfunction/dysregulated innate immune response - not infective despite the name
Pathergy - new/worsening lesions at sites of trauma/surgery (important reason to avoid surgical debridement)
Associated conditions: IBD (Crohn's/UC), rheumatoid arthritis, haematological malignancy (esp. myeloproliferative disorders/MGUS), other autoinflammatory conditions

Diagnosis

Diagnosis of exclusion - clinical (violaceous undermined border, rapidly enlarging, disproportionately painful) + exclusion of infection, vasculitis, malignancy, venous/arterial disease
Biopsy shows neutrophilic infiltrate but is non-specific - mainly used to exclude mimics (infection, malignancy, vasculitis)
Screen for associated systemic disease (IBD symptoms, joint symptoms, FBE/blood film for haematological association)

Management

Avoid surgical debridement/excision - pathergy risk worsens the ulcer
Systemic corticosteroids first-line for significant disease; ciclosporin as steroid-sparing alternative
Biologic therapy (anti-TNF, esp. infliximab) for refractory disease or when associated IBD present - treats both conditions
Gentle wound care, avoid aggressive dressing changes/trauma
Treat the underlying associated systemic disease where identified

Associations

Inflammatory bowel disease (commonest association), rheumatoid arthritis, myeloproliferative disorders, monoclonal gammopathy (MGUS)
Peristomal pyoderma gangrenosum in IBD patients with stomas

Natural history & complications

Can progress rapidly if untreated or if surgically debrided (pathergy)
Responds to immunosuppression in most cases but scarring is common
Recurrence possible, particularly if underlying systemic disease remains poorly controlled

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