Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder characterized by muscle weakness and fatigue. It is categorized as a neuromuscular junction disorder, specifically a myasthenic syndrome, which affects the communication between nerves and muscles.
In LEMS, the body's immune system mistakenly attacks the voltage-gated calcium channels (VGCCs) located on the nerve endings that release the chemical messenger acetylcholine. These VGCC antibodies disrupt the normal functioning of the neuromuscular junction, leading to impaired communication between nerves and muscles. As a result, affected individuals experience muscle weakness that typically starts in the legs and progresses to other muscle groups.
Common symptoms of Lambert-Eaton myasthenic syndrome include muscle fatigue, difficulty walking, reduced reflexes, drooping eyelids (ptosis), bladder and bowel dysfunction, dry mouth, and problems with coordination. The weakness tends to improve with repetitive use of the affected muscles due to a distinct feature of LEMS known as the "facilitation phenomenon." Certain activities or medications that enhance the release of acetylcholine can temporarily alleviate the muscle weakness.
LEMS is often associated with an underlying malignancy, particularly small cell lung cancer. However, it can also occur in individuals without an underlying tumor. It is diagnosed through a combination of clinical symptoms, electrophysiological tests, and the presence of VGCC antibodies in blood samples.
Treatment for LEMS involves addressing the underlying cause, if present, and managing the symptoms. Medications that enhance acetylcholine release or inhibit its breakdown, such as 3,4-diaminopyridine or pyridostigmine, are commonly prescribed to improve muscle strength and function. Additionally, immunosuppressive therapy may be employed to suppress
