Plasma exchange and immunosuppressive drug treatment in the Lambert-Eaton myasthenic syndrome.

We undertook serial clinical and electromyographic muscle action potential (MAP) amplitude assessments in nine patients with the Lambert-Eaton myasthenic syndrome (LEMS) over 0.5 to 2.5 years who received plasma exchange (PE; 5 to 15 exchanges over 4 to 19 days) and immunosuppressive drug (IS) treatment (prednisolone 60 to 100 mg on alternate days, azathioprine 2.5 mg/kg for 0.5 to 2.5 years), and who had no signs of carcinoma at entry. Eight patients responded to PE. The peak MAP response occurred 10 to 15 days post-PE, representing a 2.5-fold mean increase and was significant (p less than 0.01). Two of three patients who developed carcinoma responded initially to IS. Three of six noncarcinoma patients developed sustained clinical and MAP remission after 0.5 to 1 year; the three others, of whom two were intolerant of azathioprine, improved. IS and PE may benefit LEMS patients, but caution is required when carcinoma risk is high.