Lambert-Eaton Myasthenic Syndrome BMJ Best Practice
Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder of the neuromuscular junction. LEMS occurs either as a paraneoplastic disorder in association with an underlying cancer (CA-LEMS), or without cancer and as part of a more general autoimmune state (NCA-LEMS). Symptoms include insidious and gradual onset of fatigue, weakness, and a dry mouth. Clinical findings include proximal muscle weakness in hip girdle and thigh muscles; absent or reduced tendon reflexes that may facilitate after brief exercise; and dilated, poorly reactive pupils. Serum P/Q-type voltage-gated calcium-channel antibodies are usually present. Electrophysiologic studies usually demonstrate decremental responses to low-frequency repetitive nerve stimulation, and may also exhibit postactivation facilitation of >100%. Over 40% of patients with LEMS have underlying cancer, usually small cell lung cancer. Effective treatment of underlying cancer frequently improves symptoms. Effective symptomatic and long-term treatment options include agents that augment neuromuscular transmission and immunomodulators. However, many patients have long-term disability due to weakness.
