[Anti-voltage-gated calcium channel antibodies in the Lambert-Eaton myasthenic syndrome].

We have tested 29 patients with the Lambert-Eaton myasthenic syndrome (LEMS) for serum antibodies to voltage-gated calcium channels (VGCC) using an immunoprecipitation assay in which [125]-omega-conotoxin GVIA is used to label calcium channels extracted from IMR-32, a human neuroblastoma cell line. Fifty-five percent of these patients had significant levels of antibody [31.6 (26.5, 48.2) (med., Q1, Q3) pmol/L, n = 29], compared with healthy controls [21.5 +/- 3.4 (mean +/- SD) pmol/L, n = 30] and other neurological disorders [25.2 +/- 4.2 (mean +/- SD) pmol/L, n = 10]. These antibodies were found in 43% of the patients with small cell lung carcinoma (SCLC) without signs and symptoms of LEMS [32.2 +/- 7.2 (mean +/- SD) pmol/L n = 30] and 7% of the myasthenic patients [21.4 +/- 6.8 (mean +/- SD) pmol/L n = 14]. Anti-VGCC antibody titers did not correlate with presence of SCLC, disease duration, or an electromyographic index of disease severity. Our results suggest that the antibodies detected in this assay are specific to some patients with LEMS, but not all. This assay is a useful aid in diagnosing LEMS but has much room for improvement.