Inclusion Criteria:  Patient corresponding to one of the two following groups:  Systemic autoimmune pathology known to be complicated by small fiber neuropathies.  The following autoimmune pathologies will be included: Lupus, Sjogren, Scleroderma, Myositis, rheumatoid arthritis, Sarcoidosis, Vasculitis of small or medium vessels  No conditions known to be responsible at SFN, unexplained pain symptoms Aged ≥ 18 years Having given free and informed written consent  Exclusion Criteria:  Chronic alcoholism Unbalanced diabetes Chemotherapies HIV Vitamins B12, B1, B6 deficiencies