Small-diameter nerve fiber neuropathy in systemic lupus erythematosus.

BACKGROUND Systemic lupus erythematosus (SLE) is an inflammatory, autoimmune, multiorgan disease often involving the central and peripheral nervous systems. OBJECTIVE To determine whether there is a selective small-diameter nerve fiber neuropathy in patients with SLE. DESIGN Cross-sectional study. SETTING Stavanger University Hospital, Stavanger, Norway. Patients Sixty patients with SLE, aged 43.2 +/- 13.5 years (mean +/- SD). INTERVENTIONS Skin biopsies, nerve conduction studies, and clinical neurologic examinations. MAIN OUTCOME MEASURES Density of intraepidermal small-diameter nerve fibers in skin biopsy specimens and large-diameter nerve fiber function as determined by nerve conduction studies and clinical examinations. RESULTS The mean density of intraepidermal small-diameter nerve fibers in patients with SLE was 7.5 +/- 3.8/mm. Eight patients (13%) had densities below reference values, consistent with small-diameter nerve fiber neuropathy, and results of nerve conduction studies were normal in 6 of them. Eleven patients (18%) had abnormal results of nerve conduction studies, reflecting large-diameter nerve fiber neuropathy, and 4 patients (7%) were classified by an experienced neurologist as having polyneuropathy after the clinical examination. CONCLUSIONS An abnormal reduction in intraepidermal small-diameter nerve fiber densities is evident in some patients despite normal function of their larger nerve fibers. This adds further support to the theory that a pure small-diameter nerve fiber neuropathy may occur in SLE.