Allergic vasculitis induced by hydrochlorothiazide: confirmation by mast cell degranulation test.

A case of allergic vasculitis of the skin following long-term treatment with hydrochlorothiazide is described. The etiopathogenic role of hydrochlorothiazide is strongly suggested by clinical evidence. The positive mast cell degranulation test to hydrochlorothiazide suggests the possible role of immunological in vitro tests in the diagnosis of drug eruption.