Harvey's Garden

Pyoderma gangrenosum

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4 min read

Epidemiology & Risk Factors

  • Peak incidence: 40–60 years; slight female predominance.
  • Systemic disease associations (present in >50% of pts):
    • Inflammatory Bowel Disease (IBD): Ulcerative Colitis > Crohn disease (course of PG often independent of intestinal disease activity).
    • Inflammatory arthritis: Rheumatoid arthritis (RA), seronegative spondyloarthropathies.
    • Hematologic disorders: Acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), monoclonal gammopathy of undetermined significance (MGUS).
  • Pathergy: Development or worsening of lesions following minor local cutaneous trauma (e.g., needle sticks, biopsy, surgical debridement).

Clinical Features

  • History:
    • Rapidly progressive, severely painful skin breakdown.
    • Often preceded by minor trauma (iatrogenic or accidental).
  • Physical Examination:
    • Initial lesion: Tender erythematous papule, pustule, or vesicle.
    • Progression: Rapid expansion and necrosis into an ulcerative lesion.
    • Ulcer characteristics:
      • Violaceous, purplish, undermined borders. c
      • Base is purulent, necrotic, and exudative with vegetative granulation tissue.
    • Classic location: Pretibial region (shins); can also occur on trunk, peristomal sites, or head/neck.

Diagnosis

  • Initial/Screening:
    • Primarily a clinical diagnosis of exclusion.
    • Wound swab/Gram stain and culture (bacterial, fungal, mycobacterial) to rule out active primary infection (cultures are typically sterile).
  • Skin Biopsy:
    • Performed to rule out infection, malignancy, and true vasculitis.
    • Findings: Dense, neutrophilic dermatosis (neutrophilic infiltrate in the dermis) with tissue necrosis; absence of primary leukocytoclastic vasculitis.
    • Precaution: May induce pathergy; perform only if alternative diagnoses are strongly suspected and with caution.
  • Confirmatory / Gold Standard:
    • No definitive laboratory or histopathologic test; relies on validated diagnostic criteria (e.g., Delphi consensus criteria: neutrophilic infiltrate on bx + exclusion of infection + ≥4 minor criteria including rapid progression, pathergy, cribriform scarring, systemic disease).
  • Workup for Underlying Etiology:
    • Colonoscopy (screen for occult IBD).
    • CBC, peripheral smear, serum protein electrophoresis (SPEP) (screen for hematologic dyscrasias).
    • Inflammatory markers: ↑ ESR, ↑ CRP.

Differential Diagnostics

  • Ecthyma Gangrenosum:
    • Differentiating features: Seen in severely neutropenic/immunocompromised pts; caused by Pseudomonas aeruginosa bacteremia; begins as hemorrhagic bullae evolving into a painless or tender necrotic ulcer with a black eschar; blood cultures are positive.
  • Erythema Nodosum:
    • Differentiating features: Also associated with IBD/sarcoidosis, but presents as tender, erythematous, non-ulcerating subcutaneous nodules on the anterior shins; biopsy shows septal panniculitis without dermal necrosis.
  • Necrotizing Fasciitis:
    • Differentiating features: Acute surgical emergency presenting with systemic toxicity, hemodynamic instability, crepitus, and pain out of proportion; requires immediate aggressive surgical debridement (contrast with PG, where debridement is strictly contraindicated).
  • Venous Stasis Ulcer:
    • Differentiating features: Typically located over the medial malleolus, painless or dull ache, associated with chronic venous stasis signs (hemosiderin deposition, lipodermatosclerosis, stasis dermatitis, varicosities); lacks violaceous undermined borders.
  • Calciphylaxis (Calcific Uremic Arteriolopathy):
    • Differentiating features: Seen in pts with ESRD on hemodialysis, hyperparathyroidism, or warfarin use; extremely painful ischemic purpura progressing to non-healing black necrotic eschars, often in areas with high adipose tissue (thighs, abdomen); vascular calcification on imaging/biopsy.

Management

  1. Crucial Principle:
    • DO NOT perform surgical debridement (triggers pathergy and leads to rapid, massive wound enlargement).
  2. First-Line (Mild/Localized disease):
    • High-potency topical corticosteroids (e.g., clobetasol 0.05% ointment) OR topical calcineurin inhibitors (e.g., tacrolimus 0.1% ointment).
    • Intralesional triamcinolone injections at the active border.
    • Gentle wound care with non-adherent dressings.
  3. First-Line (Extensive, rapidly progressive, or refractory localized disease):
    • Systemic corticosteroids: Oral prednisone (0.5–1.0 mg/kg/day) or IV pulse methylprednisolone for rapid control.
  4. Second-Line / Steroid-Sparing Agents:
    • Cyclosporine (often combined with systemic steroids for synergistic response).
    • Biologic therapy: TNF-alpha inhibitors (e.g., infliximab, adalimumab); preferred agent if concurrent active IBD or RA.
  5. Refractory Disease:
    • Mycophenolate mofetil (MMF), azathioprine, IVIG, or cyclophosphamide.
  6. Underlying Disease Optimization:
    • Treat comorbid conditions (IBD, RA, malignancy), though PG remission does not always correlate with underlying disease control.

Complications

  • Secondary bacterial superinfection and sepsis.
  • Extensive disfigurement and cribriform (sieve-like) scarring.
  • Chronic non-healing wounds leading to functional disability.
  • Complications of prolonged systemic corticosteroid and immunosuppressive therapy (e.g., opportunistic infections, osteoporosis, hyperglycemia).

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