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
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Purpura with organ injury or necrosis
Fever and shock, haemoptysis, hypoxia, haematuria with renal decline, severe abdominal pain or bleeding, new foot drop, rapidly expanding bullae, retiform necrosis or a cold painful limb is not safely classified as skin-limited vasculitis.
Action: Arrange emergency hospital assessment, culture and treat possible infection before immunosuppression, and involve dermatology with renal, respiratory, gastrointestinal, neurology, rheumatology, haematology or vascular teams according to the threatened organ.
Synopsis
Diagnose cutaneous small-vessel vasculitis through lesion chronology and clinicopathological correlation, protect ulcerated skin, identify removable triggers, and recognise when the eruption is a marker of systemic disease.
Cutaneous small-vessel vasculitis is a clinicopathological pattern of inflamed superficial dermal vessels, most often presenting as symmetrical palpable purpura on dependent legs.
Describe crops, age, elevation, blistering, pustules, ulcers and residual pigment; confluent angular necrosis suggests an occlusive vasculopathy or deeper-vessel process instead.
A dermatology assessment links each visible lesion to the sample required: a newly developed intact papule for full-depth H&E and a separate very early lesion for direct immunofluorescence.
Key red flags
Toxic illness, rapidly advancing purpura, severe pain, necrosis, haemorrhagic bullae, proteinuria or haematuria, rising creatinine, haemoptysis, breathlessness, abdominal bleeding, focal weakness or constitutional loss demands expedited systemic investigation.
Systemic vessel signal
Haemoptysis, renal decline, bowel ischaemia or bleeding, mononeuritis, fever and weight loss indicate disease beyond cutaneous venules.
Investigation priorities
01
H&E punch from a new papuleFirst step
Confirm inflammatory small-vessel damage and assess depth and competing pathology.
Management branches
First-line dermatology sequencePhotograph, time and pair the samples
New palpable purpura is stable enough for an outpatient or ward diagnostic pathway.
Map lesion crops and organ symptoms, record blood pressure and urine and photograph representative early, established and ulcerated lesions with consent.
Select one recent intact raised papule for formalin histology and a separate freshest appropriate lesion for DIF, confirming medium and courier timing with the laboratory.
First-line skin-limited careControl dependency and protect the barrier
Initial testing is reassuring, lesions are non-necrotic and no organ syndrome is present.
Key medicines
Colchicine specialist trialUse 500 micrograms by mouth once daily initially and, if required and tolerated, increase to 500 micrograms twice daily for a defined off-label trial with an agreed stop date.
Dapsone specialist alternativeA dermatologist may begin 50 mg by mouth once daily and increase to 100 mg once daily only after baseline safety tests and early blood monitoring confirm tolerability.
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.