Patients with Lambert-Eaton myasthenic syndrome (LEMS) possess antibodies to voltage-gated calcium channels on presynaptic lower motor neurons, which decreases calcium influx and acetylcholine release to postsynaptic skeletal muscle cells.

In some patients, malignancies (eg, small cell lung cancer) trigger production of these antibodies, resulting in paraneoplastic LEMS Patients present with progressive proximal muscle weakness that improves with repetitive motion and exercise.