Inclusion Criteria:  Adult patient with an initial diagnosis of necrotizing vasculitis having a symptomatic peripheral neurological impairment, associated with systemic necrotizing vasculitis or isolated pure without further visceral impairment  Exclusion Criteria:  Symptomatic peripheral neurological impairment not attributable exclusively to necrotizing vasculitis Diabetes Chronic ethylism AL (immunoglobulin light chain) amyloidosis or TTR (transthyretin) Genetic neuropathies Toxic neuropathies Opposition to participation in the study Lack of social security Under guardianship or curatorship