Autoimmune disorders of neuromuscular transmission.

Myasthenia gravis and Lambert-Eaton syndrome are autoimmune disorders of the neuromuscular junction. The most common form of myasthenia gravis is associated with antibodies directed against the acetylcholine receptor on the postsynaptic membrane. In Lambert-Eaton syndrome, antibodies are directed against P/Q-type voltage-gated calcium channels on presynaptic cholinergic nerve terminals at the neuromuscular junction and in the autonomic nervous system. Lambert-Eaton syndrome may represent a paraneoplastic disease that is most commonly associated with small-cell lung carcinoma or an autoimmune disorder. In both myasthenia gravis and Lambert-Eaton syndrome, the approach to treatment includes symptomatic and immune therapy. Symptomatic therapy in both disorders includes acetylcholinesterase inhibitors. In Lambert-Eaton syndrome, agents that augment the quantal release of acetylcholine are also effective. Immune therapy includes immune suppression with various medications, short-term immune modulation with plasma exchange and intravenous immunoglobulin, and thymectomy in myasthenia gravis. When Lambert-Eaton syndrome is associated with cancer, the disease may improve or remit with effective treatment of the underlying malignancy. Current treatment options will be summarized for both disorders.