[How I explore. . . vasculitis of the peripheral nervous system].

Vasculitic neuropathies require early diagnosis and therapy since their prognosis is potentially severe. The following features are usually suggestive of a vasculitic neuropathy: painful multiple mononeuropathy with an acute/subacute course, signs and symptoms of multisystem involvement (arthritis, asthma, renal and skin involvement), biological evidence of an inflammatory syndrome. In one third of patients however, vasculitic neuropathies present as a polyneuropathy. For other patients, peripheral neuropathy is the presentation mode of a necrotizing vasculitis, in the absence of biological inflammatory syndrome. A combined muscle and nerve biopsy, will usually demonstrate the vasculitic process. Vasculitic neuropathies often have a favourable prognosis when immunosuppressive therapy (corticosteroids and/or cyclophosphamide) is initiated at an early stage.