Lambert Eaton Myasthenic Syndrome (LEMS) is a rare autoimmune neuromuscular disorder characterized by muscle weakness and impaired neuromuscular transmission. It is considered a subcategory of myasthenic syndromes, which are a group of disorders that involve dysfunction in the junction where nerve cells communicate with the muscles they control (neuromuscular junction).
LEMS is caused by the body's immune system mistakenly attacking the calcium channels in the nerve cells that control muscle movement. These calcium channels are essential for transmitting nerve signals to initiate muscle contractions. When they are impaired, the release of a neurotransmitter called acetylcholine is reduced, leading to muscle weakness and fatigue.
The most common symptom of LEMS is muscle weakness, often starting in the lower limbs and progressing to affect the upper limbs, neck, and facial muscles. Weakness typically improves with repeated muscle use, known as the "myasthenic syndrome" phenomenon. Other symptoms may include difficulty in coordination, fatigue, dry mouth, constipation, and drooping eyelids.
LEMS can occur either as an acquired disorder, often associated with an underlying autoimmune condition like small-cell lung cancer, or as a hereditary form that is passed down through families.
Treatment for LEMS aims to improve muscle strength and function. This usually involves the use of medications that enhance the release of acetylcholine or suppress the autoimmune response. Physical therapy and other supportive measures may also be employed to manage symptoms and improve muscle strength and overall quality of life for individuals with LEMS.
