Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder affecting the neuromuscular junction, causing muscle weakness, reduced reflexes, and autonomic dysfunction. It is often linked to antibodies against P/Q-type voltage-gated calcium channels, which impair acetylcholine release. Diagnosis involves recognizing clinical features and using serologic studies and electrodiagnostic tests to identify specific patterns, such as low compound muscle action potential (CMAP) amplitude. LEMS can be idiopathic or associated with malignancies, particularly small cell lung carcinoma (SCLC).

Managing LEMS includes treating symptoms and any underlying malignancy. The primary symptomatic treatment is 3,4-diaminopyridine (3,4-DAP), which enhances acetylcholine release. In severe cases, intravenous immunoglobulin, plasma exchange, or immunosuppression may be used. Prognosis varies; non-tumor-associated LEMS generally has a normal life expectancy with chronic symptoms, while tumor-associated LEMS has a poorer prognosis. Regular cancer screening is vital for early detection and management. Familiarity with LEMS and its diagnostic criteria is crucial for effective treatment.

Reference: Varon M, Dimachkie M. Diagnosis and Treatment of Lambert-Eaton Myasthenic Syndrome. Practical Neurology. Accessed June 28, 2024.