Cutaneous small-vessel vasculitis

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Take a time-linked history. Establish the first lesion date, evolution, pain, itch, swelling, recurrence and whether individual urticarial lesions persist beyond twenty-four hours. Ask about fever, recent sore throat or respiratory illness, dental or cardiac infection risk, travel, hepatitis exposure, bowel symptoms, urine change, breathlessness, haemoptysis, arthralgia, sicca, neuropathic pain and weight loss. Construct a medicine timeline including prescriptions, over-the-counter NSAIDs, antibiotics, supplements and intermittent drugs started during the preceding weeks.

Describe morphology precisely. Palpable purpura is raised because inflammatory oedema surrounds a leaking venule. Dependent lower legs are typical, but buttocks, trunk and arms may be involved. Photograph distribution and select intact active lesions before dressings or glucocorticoid alter them. Livedo, angular retiform purpura and infarction suggest occlusion; subcutaneous nodules suggest deeper arteries; urticarial plaques, bullae and pustules widen the immune-complex differential.

Biopsy technique determines yield. The 2026 EADV position statement favours two lesions younger than forty-eight hours. Use an active non-necrotic purpuric papule for haematoxylin and eosin histology, deep enough to include the relevant vessels; choose an early partially blanchable macule for direct immunofluorescence. Older necrotic lesions may show non-specific damage and immunoreactants disappear with time, so a negative DIF is interpreted with lesion age and clinical data.

Management begins with the cause. Stop a suspected medicine only after weighing why it was prescribed and documenting the adverse-reaction plan; treat streptococcal, endovascular, hepatitis or other infection specifically. Elevate affected legs, reduce prolonged standing, use bland emollient and appropriate dressings and offer compression only after confirming adequate arterial circulation. Topical corticosteroid or antihistamine can reduce itch but does not treat systemic vessel inflammation.

Organ involvement transfers ownership to the relevant systemic pathway. IgA vasculitis needs renal and gastrointestinal follow-up; ANCA disease requires rapid induction assessment; cryoglobulinaemia requires infection and clonal work-up; endocarditis requires antimicrobial and source-control care. Continue wound, pain and venous management while causal therapy proceeds. On follow-up, repeat urine and renal assessment and ask specifically about newly evolving organ symptoms rather than reviewing the rash alone.

Key points

The hallmark is palpable non-blanching purpura, usually in crops on dependent lower legs; vesicles, bullae, pustules, urticarial plaques, ulcers or necrosis can occur.
Cutaneous small-vessel vasculitis describes a vessel pattern and distribution, not one cause; always decide whether disease is skin-limited, systemic or secondary to infection, medicine, autoimmunity or malignancy.
At the first assessment check observations, blood pressure, urine dip, creatinine, FBC and symptoms from lungs, kidneys, bowel and nerves before calling the eruption benign.
For diagnostic confirmation, ideally take two lesions less than 48 hours old: a non-necrotic purpuric papule for routine histology and an early partially blanchable macule for direct immunofluorescence.
Routine histology showing leukocytoclasis proves small-vessel inflammation but not its cause; IgA, complement or immunoglobulin deposition and the clinical phenotype refine classification.
A single mild skin-limited episode is usually managed first by removing a credible trigger, treating infection, rest, leg elevation, skin care, analgesia and compression only when arterial supply is adequate.
Persistent, recurrent, painful, bullous or ulcerating disease needs dermatology review; colchicine or dapsone are specialist off-label steroid-sparing choices with different renal, interaction, G6PD and blood-monitoring constraints.
Systemic glucocorticoid is reserved for severe skin disease or organ involvement after infection assessment; it is not routine treatment for every purpuric crop.
Do not inject or immunosuppress a suspected infected lesion and do not use an NSAID when nephritis, gastrointestinal bleeding, significant renal disease or cardiovascular contraindication is present.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Post-infectious immune response

Bacterial or viral infection can precede skin disease by days, while endocarditis, hepatitis and other persistent infections can continue driving immune-complex deposition.

Medicine-associated disease

Antibiotics, NSAIDs, diuretics, anticonvulsants and many other medicines can trigger a delayed hypersensitivity vasculitis, so a dated exposure history is essential.

Systemic inflammatory disease

IgA vasculitis, lupus, rheumatoid disease, Sjogren disease, ANCA vasculitis and inflammatory bowel disease can first appear through cutaneous small-vessel injury.

Malignancy and idiopathic disease

Haematological disorders and solid malignancy are occasional drivers; after proportionate investigation, no cause is identified in many single self-limited episodes.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Immune-complex deposition
Circulating antigen-antibody complexes lodge in superficial dermal post-capillary venules, activate complement and attract neutrophils to the vessel wall.
2
Leukocytoclastic injury
Activated neutrophils fragment and release enzymes, producing nuclear dust, fibrinoid vessel-wall damage and endothelial permeability on routine histology.
3
Erythrocyte and fluid leakage
Damaged venules allow red cells and plasma into dependent tissue, creating non-blanching palpable purpura, oedema, vesicles or haemorrhagic bullae.
4
Dependency and hydrostatic pressure
Lower-leg distribution is amplified by venous pressure and stasis, which slow immune-complex clearance and explain why elevation and safe compression can reduce recurrence.
5
Depth determines morphology
Superficial small-vessel injury causes purpura, while retiform necrosis, nodules or large ulcers suggest occlusion or medium-vessel involvement requiring deeper sampling and broader assessment.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Palpable purpura

Raised non-blanching red-purple papules in dependent crops are the most reliable clinical hallmark of superficial cutaneous small-vessel vasculitis.

Bullous or ulcerating phenotype

Haemorrhagic vesicles, bullae and painful ulcers reflect greater vessel leakage and tissue injury and justify earlier biopsy and specialist review.

Systemic vasculitis signalRed flag

Haematuria, breathlessness, abdominal pain, bleeding, fever, weight loss or focal neuropathy accompanying purpura moves assessment beyond skin-limited disease.

Occlusive morphologyRed flag

Livedo, angulated retiform purpura, cold tissue or necrosis suggests thrombosis, embolism, cryoprotein or deeper-vessel disease rather than uncomplicated leukocytoclastic inflammation.

Medicine-linked eruption

A new medicine followed days to weeks later by symmetrical dependent crops supports a drug trigger, but infection and systemic organ disease still require assessment.

Red flags requiring action

Breathlessness, haemoptysis, falling oxygen saturation or bilateral infiltrates raises diffuse alveolar haemorrhage or infection and requires acute admission.
Haematuria, proteinuria, rising creatinine, oedema or hypertension suggests glomerulonephritis and needs urgent renal and vasculitis assessment.
Severe abdominal pain, gastrointestinal bleeding or guarding may represent bowel vasculitis, ischaemia, perforation or another surgical emergency.
New focal weakness, foot drop, asymmetric sensory loss, confusion or seizure indicates possible peripheral or central nervous-system vasculitis.
Retiform purpura, bullae, ulceration, necrosis, rapidly progressive pain or cold poorly perfused tissue suggests occlusion, deeper-vessel disease or severe inflammation.
Fever, hypotension, non-blanching rash and toxicity require an immediate sepsis and meningococcal pathway, not a delayed dermatology work-up.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line observations, urine and renal profileFirst stepFirst line
Why
Identify sepsis, hypertension and silent glomerular involvement at the initial encounter.
Interpretation and limitations
Protein, blood or casts with rising creatinine requires urgent nephrology assessment; repeat a contaminated or menstrual specimen but never dismiss a consistent nephritic pattern.
02
Reference diagnostic skin biopsies
Why
Confirm vasculitis and identify the dominant immune-deposit pattern.
Interpretation and limitations
Ideally sample two lesions under 48 hours old: a purpuric papule for routine histology and an early partially blanchable macule for DIF; lesion selection and depth alter sensitivity.
03
FBC, film, CRP or ESR, liver profile and coagulation
Why
Find infection, cytopenia, haematological disease, liver dysfunction and non-vasculitic bleeding.
Interpretation and limitations
Thrombocytopenia or coagulopathy explains flat purpura differently; eosinophilia may support drug or eosinophilic disease but is not independently diagnostic.
04
Complement, ANA, ANCA and immunoglobulin studies
Why
Classify recurrent or systemic disease using the pre-test phenotype.
Interpretation and limitations
Low complement suggests immune-complex disease; ANCA supports but never alone diagnoses AAV, and monoclonal immunofixation redirects assessment toward clonal disease.
05
Warm-handled cryoglobulins and viral serology
Why
Detect cryoprotein, hepatitis and HIV drivers when morphology or systemic findings warrant them.
Interpretation and limitations
Maintain cryoglobulin specimens warm until serum separation. Confirm active HCV with RNA and document complete HBV status before any B-cell depletion.
06
Cultures and focused organ testing
Why
Exclude infection and define suspected pulmonary, gastrointestinal, neurological or renal involvement.
Interpretation and limitations
Obtain blood cultures before antibiotics for possible endocarditis; select chest CT, nerve studies, echocardiography or organ biopsy from symptoms rather than routine scanning.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Sepsis and meningococcaemia

Acute toxicity, shock and rapidly evolving non-blanching lesions demand immediate cultures and antibiotics; biopsy must never delay life-saving infection treatment.

Thrombotic vasculopathy

Antiphospholipid disease, calciphylaxis, cholesterol emboli and livedoid vasculopathy produce retiform ischaemia through occlusion rather than primary vessel-wall inflammation.

Platelet or coagulation disorder

Flat petechiae, mucosal bleeding, thrombocytopenia or abnormal coagulation can cause non-palpable purpura without leukocytoclastic vessel injury.

IgA and urticarial vasculitis

IgA-dominant deposits with abdominal, joint or renal features and urticarial plaques persisting beyond twenty-four hours identify different immune-complex phenotypes.

Pigmented purpuric dermatosis

Chronic cayenne-pepper macules with minimal palpability and no systemic illness favour capillaritis, which lacks destructive leukocytoclastic vasculitis.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01First-line triageDecide skin-limited or systemicFirst stepFirst lineA new non-blanching palpable eruption is identified.

1Record observations and blood pressure, examine lesion morphology and perfusion and ask systematically about renal, pulmonary, bowel, neurological and infectious symptoms.
2EscalationPerform urine dip, FBC, renal and liver tests and inflammatory markers and arrange same-day escalation for toxicity, necrosis or any organ signal.
3Photograph active untreated lesions and secure appropriately timed routine-histology and DIF biopsies when confirmation will alter classification.

02Skin-limited first-line careRemove pressure and the driverFirst lineThe patient is well, baseline organ assessment is reassuring and lesions are non-necrotic.

1Review and remove a credible medicine trigger safely, treat identified infection and avoid adding an unnecessary antibiotic or immunosuppressant.
2Use rest during painful crops, leg elevation, bland emollient, appropriate dressings and compression only after arterial adequacy is established.
3Offer symptom-specific analgesia, topical corticosteroid for inflammatory itch or antihistamine, then review urine and trajectory with clear return advice.

03Persistent-disease escalationUse a measurable steroid-sparing trialEscalationCrops recur, persist, ulcerate or impair function despite cause removal and supportive care.

1Recheck diagnosis, infection, medicine exposure, venous disease and systemic features before labelling the process idiopathic or treatment-resistant.
2With dermatology, select off-label colchicine or dapsone according to kidney, interaction, G6PD, blood and reproductive safety and define a response deadline.
3EscalationUse a short systemic glucocorticoid course only for severe inflammation, taper promptly and escalate to disease-specific immunosuppression if organs are involved.

04Emergency routeTreat the dangerous alternativeAlternativeToxic illness, necrosis, pulmonary-renal findings, bowel pain or focal neurological deficit appears.

1Admit, culture and begin sepsis treatment when indicated while securing urgent dermatology, rheumatology and affected-organ assessment.
2Use vascular imaging, tissue biopsy and systemic serology in parallel to distinguish occlusive, immune-complex and pauci-immune mechanisms.
3Begin the confirmed or strongly suspected systemic-disease pathway without allowing the descriptive skin label to delay organ rescue.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

May reduce recurrent purpuric crops and pain when supportive measures and cause removal are insufficient, although controlled evidence is limited.

Colchicine for recurrent skin-limited vasculitis

A common specialist off-label trial is 500 micrograms orally once daily, increasing to 500 micrograms twice daily if needed and tolerated; review response after several weeks and stop if ineffective.

This indication is off-label. Reduce or avoid in renal or hepatic impairment, stop for diarrhoea or vomiting and check interactions with macrolides, azoles, ciclosporin, verapamil and statins because fatal toxicity, cytopenia and neuromyopathy can occur. Pregnancy or breastfeeding requires specialist product-specific review.

A neutrophil-modulating option for recurrent or persistent skin-limited disease, especially when repeated glucocorticoid would cause disproportionate harm.

Dapsone

Specialists commonly start 50 mg orally once daily and may increase to 100 mg once daily according to skin response and blood safety; cutaneous small-vessel vasculitis is an off-label indication.

Check G6PD activity, FBC, reticulocytes, liver and renal function before treatment and monitor FBC closely. Severe G6PD deficiency and severe anaemia are contraindications; haemolysis, methaemoglobinaemia, agranulocytosis, hepatitis and neuropathy require urgent review. Use in pregnancy only when benefit outweighs risk; breastfeeding can cause infant haemolysis and needs specialist review.

Provides temporary rapid control while a trigger is treated or a steroid-sparing and systemic disease plan is established; it is not routine therapy for a mild first crop.

Prednisolone for severe cutaneous inflammation

For painful necrotic, bullous or ulcerating disease after infection assessment, a common off-label regimen is about 0.5 mg/kg orally once daily for 1 to 2 weeks, tapered over a total of 3 to 6 weeks according to response.

Exclude or actively treat infection, monitor glucose, blood pressure, mood, gastrointestinal and bone risk and provide steroid-card advice. Repeated courses add adrenal suppression; pregnancy and breastfeeding usually favour prednisolone when steroid is necessary but still require individual review.

Relieves itch and superficial inflammation but does not prevent glomerulonephritis, neuropathy or other systemic vessel damage.

Topical corticosteroid

Apply an appropriate prescribed potency thinly to itchy inflamed intact skin once or twice daily for a short defined course; use lower potency on thin skin and do not apply into an ulcer unless directed.

Avoid untreated bacterial, fungal or viral infection and prolonged unsupervised use; monitor atrophy, bruising and systemic absorption over large, occluded or broken areas.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Ulceration and scarring

Bullous or necrotic injury can leave painful ulcers, secondary infection, delayed healing, dyspigmentation and permanent scar.

Systemic organ damage

Missed renal, pulmonary, gastrointestinal or neurological vasculitis can cause kidney failure, haemorrhage, bowel infarction or fixed nerve deficit.

Recurrent dependent disease

Persistent venous pressure, an untreated driver or premature withdrawal of treatment can produce repeated crops and chronic lower-leg discomfort.

Medicine toxicity

NSAIDs, glucocorticoids, colchicine and dapsone can cause renal, gastrointestinal, metabolic, marrow, neuromuscular or haemolytic harm when used without selection and monitoring.

Diagnostic delay

Labelling every purpuric eruption idiopathic can postpone recognition of endocarditis, hepatitis, connective-tissue disease or a haematological malignancy.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

At early review repeat blood pressure, urine dip and renal function and ask about haematuria, oedema, breathlessness, abdominal pain, bleeding, weakness and numbness.
Use dated photographs and a lesion diary to record new-crop frequency, pain, itch, ulcer dimensions, necrosis, infection and time spent standing.
Reconcile all recent and intermittent medicines and document a suspected culprit precisely so future avoidance does not expand to unrelated drug classes.
For ulcers, record depth, perfusion, exudate and surrounding inflammation and culture only when infection is clinically suspected rather than from every colonised wound.
During colchicine monitor gastrointestinal toxicity, renal and hepatic function, interacting medicines, muscle symptoms and FBC when prolonged treatment or risk factors apply.
During dapsone follow FBC and liver tests at the specialist-defined early interval, then periodically; check methaemoglobin when cyanosis or unexplained dyspnoea occurs.
If disease recurs after apparent resolution, reassess systemic and causal clues instead of automatically issuing another glucocorticoid course.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Biopsy two different moments

Routine histology needs a developed purpuric papule, while DIF performs best in an earlier partially blanchable lesion before immune deposits degrade.

Palpability reflects leakage

Raised purpura arises from inflammatory oedema around injured venules; flat petechiae make platelet and coagulation causes more prominent alternatives.

Retiform means rethink mechanism

Angular branching necrosis maps an occluded vascular network and should prompt thrombosis, embolism, calciphylaxis, cryoprotein and deeper-vessel assessment.

Skin-limited is a follow-up diagnosis

A reassuring first screen lowers risk but later kidney, bowel, lung or nerve features can reclassify the illness.

DIF names a phenotype

IgA, immunoglobulin or complement deposits refine immune-complex classification, but a negative aged-lesion DIF cannot erase convincing clinicopathological vasculitis.

Compression needs circulation

Dependency can be treated with compression only after significant arterial insufficiency and acutely ischaemic tissue have been excluded.

11Common pitfallsFrequent interpretation and management errors.

01
Calling every non-blanching rash vasculitis without checking platelets, coagulation, sepsis and occlusive mimics.
02
Biopsying only the black centre of an old necrotic lesion and then over-interpreting non-specific tissue death.
03
Ordering broad autoantibodies while omitting blood pressure, urine dip, creatinine and an organ review.
04
Starting systemic steroid for a febrile purpuric patient before obtaining cultures and addressing possible endocarditis or invasive infection.
05
Continuing a plausible trigger medicine because the rash is mild without discussing a safe substitution and adverse-reaction record.
06
Using colchicine or dapsone without renal, interaction, G6PD and blood safety checks.
07
Reassuring a patient that disease is permanently skin-limited without explicit return advice for haematuria, abdominal pain, breathlessness or weakness.