Lambert-Eaton myasthenic syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is a rare disorder of nerve-muscle (neuromuscular) junction. Both the etiology and the clinical findings of the disease may resemble myasthenia gravis, but there are many substantial differences between clinical presentations and pathogenetic features of two disorders.

Related Topics:
Neuromuscular - Myasthenia gravis

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Anderson was the first person to mention a case with possible clinical findings of LEMS in 1953, but Lambert, Eaton and Rooke were the first physicians to substantially describe the clinical and electrophysiological findings of the disease in 1966.

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LEMS usually comes out alone but lung cancer (small-cell histology) may accompany the disease in some cases. In both conditions, the disease is of autoimmune origin, that is, it is caused by antibodies that are directed against the antigens of the neuromuscular junction. In 1989, the previously anticipated antibodies were demonstrated to be directed against calcium channels, which are located in neuromuscular junction (see synapse) and are responsible from the efficient release of acetylcholine. The antibodies prevent normal function of calcium channels and thus prevent the release of acetylcholine that is essential for normal nerve-muscle interactions, which maintain the normal muscle strength (see synapse, nerve, neuron, muscle). There are also some patients that do not carry these antibodies in their serum samples and the exact cause of disease in these cases still remains to be determined. In cases with both LEMS and lung cancer (usually small cell type), the antibodies are suggested to be aimed at cancer cells and to bind and affect the antigens in neuromuscular junction accidentally. LEMS can be observed in other types of cancer including the transitional cell carcinoma of the bladder. Approximately 50% of LEMS cases have an identifiable malignancy. The disease is usually observed in middle aged and older people but children and young people can be affected, as well. Due to the infrequency of the condition, the exact incidence is unknown.

Related Topics:
Lung cancer - Synapse - Acetylcholine - Nerve - Neuron - Muscle

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