Lambert-Eaton myasthenic syndrome
| Lambert–Eaton myasthenic syndrome | |
|---|---|
| Synonyms | Lambert–Eaton syndrome, Eaton–Lambert syndrome |
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| 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. | |
| Classification and external resources | |
| Specialty | neurology |
| ICD-10 | G73.1, G70.8 |
| ICD-9-CM | 358.1 |
| DiseasesDB | 4030 |
| MedlinePlus | 000710 |
| eMedicine | neuro/181 emerg/292 |
| MeSH | D015624 |
Lambert–Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder that is characterized by muscle weakness of the limbs. It is the result of an autoimmune reaction in which antibodies are formed 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 prevalence is 3.4 cases per million. 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).
LEMS usually occurs in people over 40 years of age, but it may occur at any age. The diagnosis is usually confirmed with electromyography and blood tests; these also distinguish it from myasthenia gravis (MG), 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.
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