Lambert-Eaton myasthenic syndrome

A rare autoimmune disorder of the neuromuscular junction.

Lambert-Eaton myasthenic syndrome (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 LEMS patients 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.

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of the neuromuscular junction. It may occur as a paraneoplastic disorder in association with cancer (CA-LEMS), usually a small cell carcinoma of the lung, or may also occur without cancer, as part of a more general autoimmune state (NCA-LEMS). In both types, LEMS is characterized by the presence of circulating antibodies against voltage-gated calcium channels; these impair neuromuscular transmission by inhibiting inward calcium current and subsequently the release of acetylcholine into the synaptic cleft.