Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 27 Aug 2026Clinical review pending
!
Necrotising infection until excluded
Extreme pain, fever, shock, crepitus, rapidly advancing erythema, gas, deep fascial signs or severe immune compromise can represent necrotising soft-tissue infection. Pyoderma gangrenosum can also progress fast and worsen after surgery, so either reflex debridement or reflex immunosuppression can be catastrophic.
Action: Arrange emergency surgical, dermatology and infection review with cultures, bloods and imaging where these do not delay care; resuscitate and treat credible infection immediately while agreeing the least traumatic diagnostic tissue plan and documenting the ulcer edge.
Synopsis
Recognise the rapidly painful undermined ulcer of pyoderma gangrenosum, avoid harmful trauma while excluding infection and vascular disease, investigate systemic associations, and coordinate wound and immune treatment.
Classic pyoderma gangrenosum begins as a tender pustule, papule or nodule and expands into an exquisitely painful ulcer with a dusky violaceous undermined border and purulent-looking sterile base.
On brown or black skin the active border may look deep purple, grey, brown or black; palpated overhang, warmth, oedema and rapid centrifugal change help when erythema is subtle.
Pathergy is lesion induction or worsening after minor trauma, cannulation, biopsy, stoma friction or debridement; it supports PG but is neither universal nor unique.
Key red flags
Shock, crepitus, spreading deep pain, exposed tendon or bone, critical ischaemia, uncontrolled bleeding, sepsis, ocular disease, stoma breakdown, rapidly expanding bullae, cytopenia or constitutional loss requires same-day multidisciplinary assessment.
Bullous haematological pattern
Superficial blue-grey bullae and erosions, often on upper limbs or face, are associated with myeloid malignancy and require urgent haematological assessment.
Investigation priorities
01
Serial examination and photographsFirst step
Document rate, edge morphology and treatment response while reducing repeated traumatic handling.
Management branches
First emergency decisionHold infection and PG in view together
A painful ulcer is expanding quickly or worsens after a procedure.
Assess ABCDE, pain, crepitus, perfusion, fascial signs and systemic toxicity and take photographs and cultures without slowing treatment of suspected sepsis.
Convene surgical, dermatology and infection review early; operate urgently for credible necrotising infection while avoiding serial margin debridement driven only by sterile postoperative expansion.
First-line local treatmentCalm a small active border atraumatically
PG is localised and slowly progressive without deep exposure or major systemic illness.
Key medicines
Clobetasol propionate 0.05% local therapyApply a thin dermatologist-directed layer once daily to the active inflammatory border of a small ulcer for a defined two-to-four-week induction, then reassess before continuing or tapering.
Prednisolone systemic inductionThe UK STOP GAP regimen used 0.75 mg/kg by mouth once daily, capped at 75 mg daily, with subsequent adjustment and taper according to inflammatory arrest and healing.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.