Lambert-Eaton myasthenic syndrome (LEMS) is a chronic autoimmune condition in which the signaling between the nerves and muscle cells is disrupted. There are several factors that may affect the prognosis of LEMS.

What causes LEMS

In LEMS, antibodies produced by the body mistakenly attack nerve cell endings. This blocks the release of the neurotransmitter or cell-signaling molecule acetylcholine, which normally conveys nerve signals to muscles.  Due to the shortage of acetylcholine, muscles do not receive messages to contract or relax. This results in muscle weakness, primarily in the legs and arms, and in general fatigue and other symptoms. As the condition progresses, it may affect mobility, cause difficulties in daily activities, and affect the individual’s quality of life.

It is not known what causes the body to start producing these autoantibodies. But in half of the cases, this process can be triggered by small cell lung cancer (SCLC). In SCLC, the body produces antibodies to fight off the cancer, but these antibodies cross-react with proteins on nerve cell endings.

Factors affecting prognosis

The prognosis of LEMS is variable, and depends on various factors, including symptom severity and the presence of cancer.

The life expectancy of LEMS patients without underlying cancer is a normal one. The progression of LEMS is usually slow, and symptoms worsen after months of onset. In general, people with LEMS respond well to treatments, such as immunosuppressive therapy, and about 43% achieve complete remission. However, most patients sustain some long-term disability, which can affect their quality of life.

The presence of underlying lung cancer negatively influences the prognosis of LEMS, and cancer adds to the complexity of LEMS treatment. Prognosis also is dependent on the patient’s response to cancer treatment. The long-term survival rate of people with SCLC and LEMS is generally poor, with a median survival period of 17 to 24 months. However, some studies have shown that people with SCLC have a better prognosis when the cancer is associated with LEMS. This has been attributed to the early detection of tumor in these patients.

Last updated: July 22, 2019


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