Leukocytoclastic vasculitis

Anaphylactoid purpura, Cutaneous leukocytoclastic vasculitis, Purpura rheumatica, Cutaneous small-vessel vasculitis, Hypersensitivity angiitis.

Immune complex-mediated small-vessel vasculitis of the skin, typically presenting with palpable or petechial purpura.

The international incidence is approximately 20 per 100,000 people per year, with no significant gender difference. Swiss-specific prevalence data is lacking, but patterns are comparable to European cohorts. Most common in adults over 50 years; in children, it typically presents as IgA-associated vasculitis (Henoch-Schönlein purpura).

By clinical pattern:

• Hemorrhagic type
• Hemorrhagic-necrotic type
• Papulonecrotic type

By etiology:

• Infection-associated
• Drug-induced
• Autoimmune disease-associated
• Neoplasia-associated

By immunoglobulin involvement:

• IgA-associated vasculitis
• Non-IgA-associated vasculitis

By clinical course:

• Acute
• Chronic-recurrent

After infections or antigen exposure, immune complexes form and deposit in postcapillary venules of the skin, leading to complement activation and neutrophilic infiltration. Common triggers include bacterial or viral infections, medications (e.g., β-blockers, allopurinol, TNF-α inhibitors), malignancies, and autoimmune diseases. VEXAS syndrome is also associated with cutaneous vasculitis in a subset of patients.

Most commonly presents with palpable purpura on the lower legs, often accompanied by pain or pruritus. Systemic symptoms may include arthralgia, fatigue, myalgia, fever, and headache. In IgA-associated vasculitis (Henoch-Schönlein purpura): classic triad of purpura, arthralgia, and abdominal pain; renal involvement is more common in adults.

• Thorough history (recent infections, new medications, comorbidities)
• Clinical examination (bilateral palpable purpura on lower limbs)
• Skin biopsy: H&E staining and direct immunofluorescence (IgA, IgG, C3)
• Laboratory tests: CRP, ESR, full blood count, renal and liver function, ANA/ENA, ANCA, complement factors, urinalysis, cryoglobulins, hepatitis B/C and HIV serology
• Imaging studies in case of suspected systemic involvement
• Interdisciplinary assessment if organ involvement suspected

Primarily lower legs; less commonly arms or trunk. Upper body involvement may suggest systemic vasculitis.

Sudden onset a few days after infection or drug exposure. Recurrent episodes may occur in the context of chronic underlying conditions.

Fibrinoid necrosis of vessel walls, perivascular neutrophilic infiltrates, leukocytoclasia, erythrocyte extravasation, siderophages. Direct immunofluorescence reveals deposits of IgA, IgG and/or C3 in vessel walls.

• Chronic or relapsing course
• Ulceration with secondary bacterial infection
• Renal involvement (especially in IgA-associated forms)
• Rare visceral involvement (lung, gastrointestinal tract)
• Adverse effects of systemic immunosuppressive therapy

In mild cases, spontaneous resolution within 4–6 weeks. Chronic or relapsing courses require long-term follow-up. Adults with IgA vasculitis have an increased risk for long-term renal complications.

No primary prevention. Secondary prevention includes identifying and avoiding known triggers and optimal management of underlying diseases.

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3. Walls AC, Faletsky A, Chu B, et al. Epidemiology and diagnostic classification of adults presenting with an initial episode of leukocytoclastic vasculitis: a multicenter review of 440 patients. J Am Acad Dermatol. 2023;89:582-584. 
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9. Johnson EF, Wetter DA, Lehman JS, et al. Leukocytoclastic vasculitis in children: 56 biopsy-confirmed cases. J Eur Acad Dermatol Venereol. 2017;31:544-549.