Differences between myasthenia gravis and Lambert -eton syndrome.
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Myasthenia gravis is an autoimmune disorder that affects approximately 3 out of 10,000 people. Myasthenia gravis affects the neuromuscular junction (NMJ) and produces weakness of voluntary muscles. In some cases, it may be associated with tumors of the thymus (a tissue of the immune system). It also may be associated with thyrotoxicosis, rheumatoid arthritis, systemic lupus erythematosus, and other immune system disorders. In many cases, no other disorder is identified. Myasthenia gravis (MG) is most common in adult women. The exception to this is when MG is associated with thymus tumor, which is most common in elderly men.
Lambert–Eaton myasthenic syndrome (LEMS) is a rare disorder of neuromuscular transmission. Unlike MG, where the neurotransmitter (the chemical that transmits impulses) is blocked because of antibodies, LEMS is caused by an insufficient release of neurotransmitter by the nerve cell. The typical symptoms in LEMS are very similar to the generalized symptoms of MG but there are some important differences in disease progression. LEMS may initially be misdiagnosed as MG because of the similarities.
LEMS was first described in association with lung cancer. The true incidence of LEMS in the United States is unknown. It is estimated that approximately 3% of patients with small cell lung cancer are affected, or approximately 4 per 1 million people in the United States. This estimate does not consider the number of patients with LEMS who do not have small cell lung carcinoma or any identifiable malignancy. Unlike MG, which affects mostly women, LEMS primarily affects men over the age of 40 years.
Electrodiagnostic studies are used in the diagnosis of MG and LEMS. This article defines the standards, guidelines, and options for electrodiagnostic studies in these diseases.