Lambert Eaton myasthenic syndrome

LEMS is a disorder of the immune system, also known as an autoimmune disorder. Autoimmune disorders occur when the body's defense system against foreign organisms (antibodies) attack healthy tissue. LEMS occurs when part of the neuromuscular junction is damaged. The neuromuscular junction is the area between a nerve cell and a muscle cell, where communication occurs through the release of a chemical signal, called acetylcholine (ACh). This results in muscle contraction or movement. When individuals have LEMS, this process is blocked and ACh is not effectively released from nerve cells.^[1][2]

In instances where LEMS is associated with cancer, the cause may be related to the body’s attempt to fight the cancer and accidental attack of nerve fiber endings, especially the voltage-gated calcium channels found there. The trigger for the cases not associated with cancer is unknown.^[1][3]

The answer to this question is complex. While the condition is not known to follow a specific pattern of inheritance, there appears to be a genetic predisposition to autoimmune diseases in general.^[4] Families with a history of Lambert Eaton myasthenic syndrome may benefit from consulting with a genetics professional. 

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by GeneTests, the American College of Medical Genetics, and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.