Overview

LEMS symptoms usually begin with leg weakness, often followed by weakness in the muscles of the eyes, face and throat. Sometimes the weakness temporarily improves after exertion.

What is Lambert-Eaton myasthenic syndrome (LEMS)?

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease — a disease in which the immune system attacks the body's own tissues. The attack occurs at the connection between nerve and muscle (the neuromuscular junction) and interferes with the ability of nerve cells to send signals to muscle cells.

The disease is named for Edward Lambert and Lee Eaton, neurologists at the Mayo Clinic in Rochester, Minn., who first described myasthenic syndrome in the 1950s and '60s.

What are the symptoms of LEMS?

Initially, LEMS can cause leg weakness and difficulty walking. Like myasthenia gravis (MG), it also can result in weakness of the eye muscles and those involved in talking, swallowing and chewing.

The main clinical difference between MG and LEMS is that in MG, the person gets weaker with exertion, and in LEMS, the person gets stronger, at least temporarily. For more, see Signs and Symptoms.

What causes LEMS?

In about 60 percent of cases, LEMS is associated with an underlying disease, particularly small-cell lung cancer. It is thought that the body's attempt to fight the cancer inadvertently causes it to attack nerve-fiber endings.

In the other 40 percent of cases, the cause is unknown. For more, see Causes/Inheritance.

What is the progression of LEMS?

LEMS usually appears in middle age, but it also can have its onset in childhood. It is more common in men than women. The progression of LEMS depends on whether it occurs with cancer, although it is treatable in all its forms. LEMS that occurs in childhood is not associated with cancer.

What is the status of research on LEMS?

MDA-supported scientists in countries around the world are working to reveal numerous facets of LEMS, from identifying possible causes and triggers to the disease's molecular underpinnings to specific treatment strategies.

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