Lambert-Eaton Myasthenic Syndrome (LEMS)
Signs and Symptoms
Lambert Eaton myasthenic syndrome (LEMS) is a rare neuromuscular disorder that weakens and fatigues the body's voluntary muscles (those we can move at will). Unlike myasthenia gravis, it may also cause mild involvement of the autonomic nervous system, a part of the nervous system that is beyond the ability of the individual to control. Like MG, LEMS does not affect the heart or major organs unless there is an associated cancer.
LEMS can affect many muscles, but usually it causes weakness mostly in the upper legs and hips more than the upper arms and shoulders. These proximal muscles are more likely to fatigue with use, and muscle fatigue and sometimes stiffness may be more prominent than actual weakness. The legs are particularly affected. There may be difficulty getting out of a chair, going up stairs, running, or walking. Lifting and pushing may be difficult.
As with MG, LEMS may also affect muscles of the eyelids causing eyelid drooping (ptosis), and it occasionally affects muscles that move the eyes resulting in double vision (diplopia) — but these symptoms are usually mild. Occasionally, there is weakness in the face and sometimes in muscles that allow for chewing, swallowing, and breathing as may occur in MG. Involvement of the autonomic nervous system is most likely to cause a dry mouth due to decreased saliva, and sometimes erectile dysfunction occurs in men.
About half of those with LEMS have or will develop cancer, especially a lung cancer called small cell. Most of these individuals are smokers. The other half of LEMS patients, who tend to be younger, do not develop cancer.
The proximal weakness is usually slowly progressive. Weakness and fatigue in LEMS can fluctuate from day to day. Stress, heat and lack of sleep may make symptoms worse. Medications (see Medical Management) can help in the management of disease. Over the long term, people without cancer usually do well with treatment, but most continue to have some symptoms. Breathing or swallowing problems are relatively rare and tend to occur later. Individuals with cancer have a more progressive course.