Lambert–Eaton myasthenic syndrome

Lambert–Eaton myasthenic syndrome
Lambert–Eaton myasthenic syndrome
Other names	Lambert–Eaton syndrome, Eaton–Lambert syndrome, myasthenic syndrome, carcinomatous myopathy
	Neuromuscular junction. Lambert–Eaton myasthenic syndrome is caused by autoantibodies to the presynaptic membrane. Myasthenia gravis is caused by autoantibodies to the postsynaptic acetylcholine receptors. Presynaptic terminal; Sarcolemma; Synaptic vesicle; Nicotinic acetylcholine receptor; Mitochondrion;
Specialty	Neurology
Frequency	3.4 per million people

Lambert–Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder characterized by muscle weakness of the limbs. It is also known as myasthenic syndrome, Eaton–Lambert syndrome, and when related to cancer, carcinomatous myopathy.

Around 60% of those with LEMS have an underlying malignancy, most commonly small-cell lung cancer; it is therefore regarded as a paraneoplastic syndrome (a condition that arises as a result of cancer elsewhere in the body). It is the result of antibodies against presynaptic voltage-gated calcium channels, and likely other nerve terminal proteins, in the neuromuscular junction (the connection between nerves and the muscle that they supply). The diagnosis is usually confirmed with electromyography and blood tests; these also distinguish it from myasthenia gravis, a related autoimmune neuromuscular disease.

If the disease is associated with cancer, direct treatment of the cancer often relieves the symptoms of LEMS. Other treatments often used are steroids, azathioprine, which suppress the immune system, intravenous immunoglobulin, which outcompetes autoreactive antibody for Fc receptors, and pyridostigmine and 3,4-diaminopyridine, which enhance the neuromuscular transmission. Occasionally, plasma exchange is required to remove the antibodies.

The condition affects about 3.4 per million people. LEMS usually occurs in people over 40 years of age, but may occur at any age.

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