Efficacy of intravenous immunoglobulin for treatment of Lambert-Eaton myasthenic syndrome without anti-presynaptic P/Q-type voltage-gated calcium channel antibodies: a case report.

We evaluated the efficacy of intravenous immunoglobulin (IVIg) in a patient with Lambert-Eaton myasthenic syndrome (LEMS). Comprehensive clinical and electrophysiological testing was performed on a 34-year-old woman with progressive limb weakness, before and after IVIg treatment. Neurological examination revealed muscle weakness, predominantly in the proximal parts of the limbs. Muscle weakness improved following a short period of maximum voluntary muscle contraction. A repetitive low-rate (3-Hz) nerve stimulation test of the abductor hallucis was normal, but high-rate (20-Hz) stimulation induced an incremental response. Anti-presynaptic P/Q-type voltage-gated calcium channel (P/Q-VGCC) antibodies were absent in the patient's serum. Whole body computed tomography revealed no tumors. We diagnosed seronegative LEMS without tumor and treated the patient with IVIg. Both clinical and electrophysiological indices improved gradually after treatment. This case study indicates that treatment with IVIg is equally effective for LEMS that is seronegative or seropositive for P/Q-VGCC antibodies.