Successful treatment of Lambert-Eaton myasthenic syndrome in a small cell lung cancer patient using 3,4-diaminopyridine: A case report.

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of the neuromuscular junction that is characterized by muscle weakness. LEMS is usually associated with cancer, most commonly small cell lung cancer (SCLC). The potassium-channel blocker 3,4-diaminopyridine (3,4-DAP), has been previously used for the symptomatic treatment of LEMS. 3,4-DAP increases the release of acetylcholine and prolongs the duration of nerve action potentials at the presynaptic membrane of the neuromuscular junction. The present study describes the case of a patient with LEMS and SCLC, for which the symptoms did not improve with anticancer therapy, but did so markedly following treatment with 3,4-DAP. The present study illustrates that 3,4-DAP is a useful treatment choice in patients with LEMS, particularly for patients who do not fully improve following anticancer therapy.