Pyoderma Gangrenosum

Pyoderma gangrenosum is a rare, painful, neutrophilic dermatosis causing rapidly enlarging necrotic ulcers, most commonly on the legs, and is a diagnosis of exclusion frequently associated with systemic disease.

1. Key History-Taking Points

Timing & Progression

• Onset & duration: since when, sudden vs gradual onset, coming and going vs constant
• Progression: is the ulcer getting larger or more painful over time?
• Previous ulcers: any prior episodes here or elsewhere on the body?
• Initiating event: did it start after minor trauma? (pathergy is characteristic of PG)

Ulcer Characteristics

• Location & size: exact site, approximate dimensions
• Pain: severity, character — PG ulcers are typically very painful
• Appearance: colour of the base, presence of black/necrotic tissue, purulent discharge, smell
• Edge: undermined, bluish-red, ragged margins are characteristic

Systemic & Associated Disease Screen

• Vascular risk factors: diabetes, hypertension, hypercholesterolaemia, smoking, prior MI/angina/stroke (arterial or diabetic ulcer)
• Neurological: pins and needles, numbness (neuropathic ulcer)
• Venous: varicose veins, DVT history, multiple pregnancies, prolonged standing
• Vasculitic & connective tissue: joint pains, skin rashes, mouth ulcers, dry eyes, Raynaud’s phenomenon, eye inflammation
• Gastrointestinal (IBD): bowel habit change, weight loss, abdominal pain, PR bleeding — IBD (especially UC) is the most common association
• Haematological malignancy: fever, drenching night sweats, lymphadenopathy, bleeding or bruising, back pain (lymphoma, leukaemia, myeloma)
• Hepatobiliary: jaundice, itch (PBC/hepatitis C associated with PG)
• Fever: may indicate secondary infection rather than primary diagnosis

Past Medical, Drug & Family History

• PMH: known IBD, RA, haematological malignancy, diabetes
• Treatments tried: wound dressings, antibiotics, steroids — response to treatment is diagnostically informative
• Family history: IBD, autoimmune disease
• Social history: occupation, mobility, living situation

2. Key Examination Findings

Inspection of the Leg & Ulcer

• Count toes — note any amputations; lift foot to inspect heels and lateral aspects; check between toes for infection
• Surrounding skin: lipodermatosclerosis, pallor, dependent rubor, shiny/hairless skin, venous eczema, varicosities
• Ulcer base: colour, depth (is bone visible?), purulent surface
• Ulcer edges: the hallmark of PG — ragged, undermined, violaceous/bluish-red edges; gangrenous (black) margin
• Signs of infection: surrounding cellulitis, erythema, warmth, discharge
• Footwear inspection
• Stoma sites: do not miss PG around a stoma (a classic PACES trap — PG may koebnerise at surgical sites)

Vascular Assessment

• Temperature gradient and capillary refill
• Peripheral pulses: dorsalis pedis, posterior tibial, popliteal
• Oedema

Neurological Assessment

• Monofilament testing: toes, metatarsal heads, heel, dorsum
• Vibration sense, joint position sense
• Ankle jerk reflexes

Targeted Systemic Examination

• Quick cardiovascular examination (signs of peripheral vascular disease)
• Abdominal examination if IBD suspected
• Lymph node examination if haematological malignancy suspected
• Inspect rest of skin and hands for arthropathy (RA, seronegative arthritis)
• Medical photography of the ulcer

3. Specific Investigations

Bloods

• Inflammatory markers: FBC, ESR, CRP
• Autoimmune screen: RF, anti-CCP, ANA, ANCA
• Haematological malignancy: immunoglobulins, serum protein electrophoresis, urine Bence Jones protein, calcium
• Hepatic screen: LFTs (to exclude PBC, hepatitis C, autoimmune hepatitis)
• Metabolic: HbA1c, fasting lipid profile (to exclude arterial/diabetic cause)

Microbiology

• Wound swabs — secondary infection is common and must be treated; bacteria isolated do not confirm infection as the primary cause

Vascular

• ABPI (ankle-brachial pressure index) — must be performed before any compression bandaging is applied

Imaging

• X-ray of the limb — to exclude osteomyelitis
• MRI — if osteomyelitis suspected on clinical grounds but X-ray negative

Histopathology

• Skin biopsy — histology is variable and often non-specific (neutrophil infiltrate, epidermal necrosis); biopsy is used primarily to exclude malignancy and other diagnoses rather than to confirm PG. PG remains a diagnosis of exclusion.

Further Investigations Based on Clinical Suspicion

• Colonoscopy if IBD suspected
• Bone marrow biopsy if myeloproliferative disorder suspected
• Medical photography — document ulcer size and appearance at baseline and follow-up

4. Management

• Urgent dermatology referral — immunosuppression and expert wound care are the cornerstones of treatment; do not delay
• Wound care: gentle debridement of necrotic tissue only; avoid wide surgical debridement during the active phase — this can dramatically enlarge the ulcer (pathergy)
• Antibiotics (e.g. flucloxacillin) only if bacteria are cultured or surrounding cellulitis is present — antibiotics do not treat the underlying condition
• Compression bandaging — careful compression can be applied if tolerated and ABPI is adequate, to reduce oedema
• Analgesia — PG is extremely painful; adequate pain relief is essential
• Topical therapies (small ulcers): potent topical corticosteroids, tacrolimus ointment, specialist dressings
• Systemic immunosuppression (larger or refractory ulcers):
  • High-dose oral prednisolone (first-line) for several weeks
  • IV methylprednisolone for 3–5 days in severe cases
  • Ciclosporin
  • Anti-TNFα agents (e.g. infliximab — particularly useful if co-existing IBD)
  • Mycophenolate mofetil, dapsone, methotrexate, cyclophosphamide, potassium iodide solution
• Treat any underlying associated condition — IBD, haematological malignancy, RA
• ICE discussion: explain the diagnostic uncertainty; outline the need to exclude common causes first (vascular, diabetic, infective); discuss referral to dermatology and the likelihood of immunosuppressive treatment

Pyoderma Gangrenosum Cheat Sheet

Pyoderma Gangrenosum Consultation Completed