Apheresis treatment in Lambert-Eaton myasthenic syndrome

The Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of peripheral cholinergic transmission in which autoantibodies decrease the presynaptic release of acetylcholine at the neuromuscular junction and autonomic system. Recent results suggest that the antibodies to P/Q-type calcium channels are the principal pathogenic factors in LEMS. Here, we present our experience with cases of LEMS who are noncarcinomatous. We studied the efficacy of plasmapheresis, analyzing the clinical score, electrophysiological finding, and the titer of anti-P/Q-type voltage-gated calcium channel (P/Q-VGCC) antibody. The first case, a 72-year-old female presenting with leg weakness, was treated by plasma exchange (PE). However, clinical improvement was transient; intravenous immunoglobulin (IVIg) therapy was followed by additional PE. She had a clinical and electromyologic improvement, and her P/Q-VGCC antibody titers decreased. Her clinical status and CMAP amplitude correlated closely with the anti-P/Q-VGCC antibody titers. The second case, a 73-year-old male presenting with leg weakness, was treated by PE and double-filtration plasmapheresis. The P/Q-VGCC antibody titres decreased immediately after these aphereses, but recovered to the pretreatment levels 1 week after them. After the immunosuppressive drugs prednisolone and azathioprine were started, his clinical symptoms improved. His antibody titers decreased gradually after immunosuppressive therapy. It is speculated that no sufficient efficacious improvement could be obtained by apheresis alone because of a high rate of P/Q-VGCC antibody production. Considering our experiences and other literature, we discuss the indication of apheresis treatment of LEMS.