Definition and epidemiology
Hypersensitivity vasculitis (HV) is the term coined by the ACR for a small-vessel, immune-complex leukocytoclastic vasculitis typically triggered by an exogenous antigen — most often a drug or, less commonly, an infection. In the 1994/2012 Chapel Hill nomenclature it is reclassified as cutaneous leukocytoclastic angiitis / single-organ cutaneous small-vessel vasculitis, reflecting that it is usually confined to the skin. It is the most common form of cutaneous small-vessel vasculitis across age groups.
A key pediatric nuance: the ACR scheme separates the two partly by age — its HSP criteria use onset ≤20 years and its HV criteria use onset >16 years, so the two deliberately overlap (there is no clean <16/>16 split). In practice, the distinction in a child rests on IgA-dominant immune deposits and systemic features (favouring HSP) versus an isolated, antigen-triggered cutaneous eruption with non-IgA or pauci-immune histology (favouring HV).
Clinical features
- Palpable purpura — the defining lesion, symmetrical and gravity-dependent (lower legs, ankles), typically appearing 7–10 days after the triggering exposure.
- Maculopapular rash, urticarial lesions, vesicles, pustules, or small ulcers may coexist.
- Lesions are often of similar age and may itch or burn; livedo and necrosis are less common.
- Systemic involvement is, by definition, minimal — its presence should prompt reclassification toward a systemic vasculitis.
Identifiable precipitants include antibiotics (penicillins, cephalosporins, sulfonamides), NSAIDs, diuretics, anticonvulsants, allopurinol, and infections (streptococcal, hepatitis B/C, HIV).
Diagnosis
The ACR 1990 classification requires a compatible illness; supportive criteria include age >16 at onset, a temporal medication trigger, palpable purpura, maculopapular rash, and a biopsy showing granulocytes around an arteriole or venule (leukocytoclasia). The presence of ≥3 of 5 criteria gives ~71% sensitivity and ~84% specificity. Confirm with skin biopsy (leukocytoclastic vasculitis on H&E; direct immunofluorescence to assess IgA vs non-IgA deposits) and screen for systemic involvement (urinalysis, renal function, FBC) and treatable triggers (infection serologies). Identify and withdraw the offending drug.
See the full criteria: Hypersensitivity Vasculitis
Red flags
- Microscopic haematuria, proteinuria, or rising creatinine — renal involvement (reclassify/escalate)
- Abdominal pain, GI bleeding, arthritis, or neuropathy — systemic vasculitis, not single-organ HV
- Necrotic or ulcerating lesions, extensive bullae
- Fever and constitutional symptoms beyond a mild reaction
- IgA-dominant deposits in a child — manage as HSP/IgA vasculitis with renal surveillance
Management overview
Management is driven by removing the cause and controlling symptoms (drug classes/strategy only):
- Identify and withdraw the trigger — discontinue the implicated drug; treat any underlying infection. This alone resolves most cases.
- Supportive care — leg elevation, rest, compression, and antihistamines or NSAIDs for symptomatic relief in skin-limited disease.
- Persistent or severe cutaneous disease — a short course of systemic corticosteroids, or agents such as colchicine or dapsone, may be used.
- Chronic/recurrent or refractory disease — a steroid-sparing immunosuppressant may be considered with specialist input.
Most antigen-triggered cases are self-limiting and resolve within weeks once the precipitant is removed; recurrent or chronic disease warrants re-evaluation for an underlying systemic disorder, connective tissue disease, or malignancy.
References
- Calabrese LH, et al. ACR 1990 criteria for hypersensitivity vasculitis. Arthritis Rheum. 1990;33:1108-1113.
- Jennette JC, et al. 2012 Revised Chapel Hill Consensus nomenclature. Arthritis Rheum. 2013;65:1-11.
- Nelson Textbook of Pediatrics, 21st ed.
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.