Differentiating the vasculitides.

The vasculitides represent a heterogeneous set of disorders that differ in prognosis and response to therapy. The initial approach to diagnosis should include distinguishing primary vasculitis from nonvasculitis disease and vasculitis associated with a separate underlying process. Subsequently, an attempt should be made to recognize the specific vasculitic disorder and initiate appropriate therapy. Diagnosis should be primarily made on the basis of the clinical pattern of disease and supported by tissue pathology, angiography, or appropriate laboratory tests.