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.