Also known as: PG, pyoderma, neutrophilic ulcerative dermatosis
Overview
Rare, non-infectious, neutrophilic dermatosis characterized by painful, rapidly progressive cutaneous ulcers with violaceous, undermined borders. It is a diagnosis of exclusion and is frequently associated with systemic disease (inflammatory bowel disease, rheumatologic disease, hematologic malignancy).
Epidemiology
Incidence 3-10 per million per year. Peak onset 40-60 years; slight female predominance. Up to 50-70% of cases are associated with an underlying systemic disorder, particularly inflammatory bowel disease (especially ulcerative colitis), rheumatoid arthritis, seronegative arthritis, IgA monoclonal gammopathy, myelodysplastic syndrome, and acute myelogenous leukemia.
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Hematologic disease: IgA monoclonal gammopathy, MDS, AML, CML, multiple myeloma
Solid tumors (less commonly)
Pathergy (lesions provoked by minor trauma, surgery, injections)
Auto-inflammatory syndromes: PAPA, PASH, PAPASH
Pathophysiology
Dysregulated innate immunity with neutrophilic infiltration produces sterile abscesses and tissue destruction. Inflammasome activation, elevated IL-1β, IL-8, IL-17, and TNF-α drive the neutrophilic response. Trauma can precipitate or worsen lesions ('pathergy') because of an exaggerated, dysregulated innate immune response at sites of injury.
Clinical presentation
Symptoms
Onset as a tender papule, pustule, or hemorrhagic vesicle that rapidly breaks down into a painful ulcer
Disproportionate pain relative to ulcer size
Predilection for the lower extremities, but can occur anywhere including peristomal skin in IBD
Pathergy: new lesions develop at sites of trauma, biopsy, debridement, or injection
Signs / physical exam
Ulcer with violaceous, dusky, undermined border and 'gunmetal' surrounding erythema
Painful, rapidly enlarging ulcer with violaceous undermined borders in a patient with IBD or RA, worsened by debridement.
Differential diagnosis
Infectious ulcer (necrotizing fasciitis, ecthyma gangrenosum, atypical mycobacteria, deep fungal) — Often single rapidly progressive lesion in immunocompromised host; cultures positive; debridement may be required
Cutaneous vasculitis — Palpable purpura, multifocal, leukocytoclastic or medium-vessel vasculitis on biopsy
Calciphylaxis — Painful retiform purpura with eschar in dialysis patient; calcium-phosphate product elevated; biopsy shows vascular calcification
Venous or arterial leg ulcer — Chronic, indolent, located on stasis-related or pressure-related sites; not violaceous undermined borders
Sweet syndrome — Pseudovesiculated tender plaques rather than ulcers; same neutrophilic dermatosis spectrum; fever and leukocytosis prominent
Diagnostic workup
Diagnostic criteria
Diagnosis of exclusion based on clinical features supported by Maverakis 2018 (PARACELSUS or modified Delphi) criteria: required major criterion is a neutrophilic infiltrate on biopsy of ulcer edge; minor criteria include exclusion of infection, pathergy, history of IBD or inflammatory arthritis, characteristic lesion morphology, rapid progression, peripheral erythema with undermined border, multiple ulcerations, cribriform scarring, and decrease in ulcer size within 1 month of immunosuppression.
Labs
CBC with differential, peripheral smear (screen for leukemia, MDS)
Serum protein electrophoresis and immunofixation (IgA monoclonal gammopathy)
ANA, RF, anti-CCP, ANCA panel
CMP, ESR, CRP
Tissue and wound cultures (bacteria, mycobacteria, fungi) to exclude infection
Age-appropriate malignancy screening; consider hematology consult if cytopenias
Imaging
Colonoscopy / GI evaluation if any bowel symptoms or peristomal lesion
Imaging tailored to suspected associations (e.g., bone marrow if cytopenias, chest CT if vasculitis is being considered)
Diagnostic algorithm
flowchart TD
A[Painful, rapidly<br/>expanding ulcer<br/>± violaceous border] --> B[Wound + tissue cultures<br/>biopsy edge for histology<br/>screen IBD/RA/MDS/IgA gammopathy]
B --> C{Infection<br/>or other cause?}
C -->|Yes| D[Treat that diagnosis]
C -->|No| E[Diagnose PG by<br/>Maverakis / clinical criteria]
E --> F{Disease severity}
F -->|Limited| G[Topical/intralesional<br/>steroid ± tacrolimus]
F -->|Moderate-severe| H[Prednisone 0.5-1 mg/kg<br/>or cyclosporine 3-5 mg/kg]
H --> I{Response<br/>at 2-4 wk?}
I -->|No| J[TNF inhibitor<br/>infliximab/adalimumab]
I -->|Yes| K[Taper slowly;<br/>treat underlying disease]
E --> L[AVOID debridement<br/>— pathergy risk]
Pyoderma gangrenosum — workup and stepwise management.
AVOID surgical debridement when possible — risk of pathergy worsens the ulcer; if grafting is undertaken, only under aggressive immunosuppression
Complications
Permanent cribriform scarring
Secondary infection of ulcers; sepsis
Pathergy-induced worsening from debridement, biopsy, or trauma
Steroid and immunosuppressant morbidity
Increased mortality compared with general population, largely from underlying systemic disease
PANCE pearls
Pyoderma gangrenosum is a diagnosis of exclusion — culture aggressively and rule out infection before immunosuppressing.
Pathergy is a defining clinical feature; avoid surgical debridement when possible, and warn patients about new lesions at trauma or surgical sites.
Always screen for IBD, inflammatory arthritis, and hematologic malignancy at diagnosis and during follow-up.
Cyclosporine and prednisone are roughly equivalent first-line systemic options (STOP GAP trial).
Cribriform 'sieve-like' atrophic scarring is the hallmark of healed lesions.
Peristomal pyoderma gangrenosum in a patient with IBD is essentially diagnostic in the right clinical context.
References
STOP GAP Trial — Ormerod AD et al. Comparison of ciclosporin and prednisolone for the treatment of pyoderma gangrenosum (BMJ 2015)
Maverakis 2018 — Diagnostic criteria of ulcerative pyoderma gangrenosum: a Delphi consensus of international experts (Maverakis et al., JAMA Dermatology 2018)
Brooklyn Trial — Brooklyn TN et al. Infliximab for the treatment of pyoderma gangrenosum: a randomised, double-blind, placebo-controlled trial (Gut 2006)
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