Lambert Eaton Myasthenic Myopathic Syndrome (LEMS) is a rare autoimmune neuromuscular disorder characterized by muscle weakness and fatigue. It is caused by an abnormal immune response that mistakenly attacks the nerve-muscle junction, impairing the communication between nerves and muscles.
In LEMS, the immune system produces antibodies that target specific calcium channels located on the outer membrane of nerve cells. These calcium channels are responsible for facilitating the release of a neurotransmitter called acetylcholine, which is essential for muscle contraction. The antibodies disrupt the functioning of these calcium channels, leading to a decreased amount of acetylcholine released into the synapse and subsequently reducing nerve signals.
The most common symptom of LEMS is muscle weakness, which primarily affects the limb muscles, especially the legs and proximal arm muscles. Muscles involved in standing up from a sitting position, walking, and climbing stairs are often affected, causing difficulty in performing these activities. Muscle fatigue is also a prominent feature, as muscle strength deteriorates with continuous exercise or prolonged activity.
LEMS is closely associated with other autoimmune diseases such as small-cell lung cancer, an underlying malignancy found in approximately half of LEMS patients. It is believed that the immune system's response to the tumor may trigger the production of antibodies that cross-react with calcium channels in the neuromuscular junction.
Treatment options for LEMS aim to increase the levels of acetylcholine in the synapse. This can be achieved through medication, specifically medications that inhibit the breakdown of acetylcholine or those that promote its release. Additionally, treating the underlying tumor if present is essential in managing LEMS. Physical therapy and supportive care are also beneficial in maintaining muscle strength and improving quality of life for individuals with LEMS.
