Hypersensitivity vasculitis

Associate Editor-In-Chief:

Hypersensitivity vasculitis (or hypersensitivity angiitis or leukocytoclastic vasculitis) is usually due to a hypersensitivity reaction to a known drug, auto-antigens or infectious agents such as bacteria. Immune complexes lodge in the vessel wall, attracting polymorphonuclear leukocytes who in turn release tissue-degrading substances leading to an inflammatory process.

Clinical Presentation
Palpable, normally painful, petechiae or purpura (skin vasculitis). The lesions normally arise in crops, with common localizations being the forearms and legs. Necrosis of skin tissue can yield lesions with black or brown centres. This disorder may affect the skin only, but sometimes affect nerves, the kidneys, joints and the heart. Renal involvement is common.

Investigations
The primary goal is to identifiy the causing agent, be it a drug or a microbe. Questioning is important, as is a thorough physical examination, chest X-ray, ESR and biochemical organ tests. Skin biopsy of the lesions reveal inflammation of the small vessels, termed leukocytoclastic vasculitis, which is most prominent in postcapillary venules. Tests for hepatitis virus, antinuclear antibodies, rheumatoid factor and cryoglobulins might be indicated.

Diagnostic Criteria
At least 3 out of 5 criteria yields a sensitivity of 71% and a specificity of 84%:


 * Age >16.
 * Use of possible triggering drug in relation to symptoms.
 * Palpable painful purpura (the three P's).
 * Maculopapular rash.
 * Skin biopsy showing neutrophil infiltration around vessel.

Treatment
The most important part of the treatment is to eliminate the cause of the vasculitis, if at all possible. Antihistamines prove helpful to some patients. If the vasculitis is damaging organ systems such as the kidneys, immunosuppressive agents are indicated.