Pyoderma gangrenosum is a rare, neutrophilic dermatosis presenting as rapidly progressive, painful ulcers with undermined violaceous borders. Pathergy is characteristic. PG is frequently associated with systemic diseases (IBD, arthritis, hematologic disorders). Diagnosis is clinical and by exclusion; biopsy supports a neutrophilic infiltrate but is not pathognomonic. Prompt anti-inflammatory/immunosuppressive therapy with wound care is essential; trauma and debridement can worsen lesions.
Epidemiology
- Incidence ~3–10 per million/year; middle-aged adults, slight female predominance.
- Associations: inflammatory bowel disease (ulcerative colitis, Crohn), inflammatory arthritis (seronegative arthritis, rheumatoid), hematologic disease (MGUS, leukemia), solid tumors less commonly.
Pathophysiology
- Dysregulated innate immunity with neutrophil dysfunction and excessive cytokines (IL-1, IL-8, TNF, IL-17).
- Pathergy: exaggerated response to minor trauma; lesions can precipitate at surgical sites or needle sticks.
Clinical Features
- Painful pustule or nodule that ulcerates rapidly into a necrolytic ulcer with undermined violaceous border and purulent base.
- Common sites: lower legs; peristomal skin, surgical wounds; can be multiple.
- Variants: classic ulcerative, bullous (hematologic malignancies), pustular (IBD flares), vegetative (superficial, indolent), peristomal.
Differential Diagnosis
- Always exclude infection: bacterial (including atypical), deep fungal, mycobacterial; vascular ulcers (arterial, venous), vasculitis, calciphylaxis, neoplasms, factitial ulcers.
- Biopsy: edge of ulcer for H&E and cultures; histology shows neutrophilic dermatosis with dermal abscess; rule out vasculitis or infection.
Diagnostic Framework
- Delphi consensus criteria (2018, updated in later reviews): major criterion—biopsy of ulcer edge showing neutrophilic infiltrate; minor criteria—exclusion of infection, pathergy, associated disease, rapid ulceration from papule/pustule, undermined violet border, multiple ulcers at least one on anterior leg, cribriform scars, decreased ulcer size with immunosuppression.
Management
- General measures
- Gentle wound care: nonadherent, moisture-balanced dressings; avoid sharp debridement during active inflammation; enzymatic/autolytic debridement preferred if needed.
- Pain control; treat secondary infection if present (but infection does not cause PG).
- Minimize trauma (pathergy precautions); stop nonessential procedures.
- Local therapy (limited superficial disease)
- High-potency topical steroids, tacrolimus ointment.
- Intralesional corticosteroids to inflammatory border.
- Compression for edema/venous disease when tolerable.
- Systemic therapy (most moderate–severe cases)
- First-line: systemic corticosteroids (e.g., prednisone 0.5–1 mg/kg/day) or cyclosporine (3–5 mg/kg/day) as steroid-sparing/alternative.
- Biologics:
- TNF inhibitors: infliximab (best RCT evidence), adalimumab; effective particularly with IBD.
- IL-1 inhibitors (anakinra, canakinumab), IL-12/23 or IL-23 inhibitors (ustekinumab, guselkumab), IL-17 inhibitors (secukinumab) have case series support.
- JAK inhibitors (tofacitinib, baricitinib) increasingly reported effective in refractory PG.
- Other immunosuppressants: mycophenolate, methotrexate, azathioprine, cyclophosphamide in select refractory cases.
- Taper carefully to avoid rebound.
- Special situations
- Peristomal PG: collaborate with stoma therapy to reduce leakage/trauma; biologics often needed.
- Postsurgical PG: recognize early to avoid repeated debridements; initiate immunosuppression.
Prognosis
- Variable; many achieve remission with appropriate immunosuppression but recurrences occur.
- Scarring common; cribriform scars characteristic after healing.
References (recent guidelines and key reviews)
- International/European consensus on PG diagnosis and treatment, 2022–2024.
- RCT and cohort data on infliximab and cyclosporine, 2021–2024.
- Systematic reviews of biologics and JAK inhibitors in PG, 2021–2025.
- Wound care best practices in neutrophilic dermatoses, 2022–2024.