Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder that affects the neuromuscular junction, causing muscle weakness and fatigue. It is also known by several other names, including:
LEMS primarily affects the voluntary muscles, such as those involved in movement and posture. The condition is characterized by muscle weakness that typically starts in the lower limbs and gradually progresses to other parts of the body. Common symptoms include difficulty walking, muscle pain, fatigue, and impaired reflexes.
The underlying cause of LEMS is the production of autoantibodies that target the voltage-gated calcium channels (VGCCs) in the neuromuscular junction. These autoantibodies interfere with the release of acetylcholine, a neurotransmitter responsible for transmitting signals between nerves and muscles. As a result, the muscles receive fewer signals, leading to weakness and fatigue.
LEMS is often associated with an underlying malignancy, particularly small cell lung cancer (SCLC). In some cases, the diagnosis of LEMS may even precede the detection of cancer, making it an important marker for further investigations.
Treatment for LEMS focuses on managing the symptoms and addressing the underlying cause. Medications such as 3,4-diaminopyridine (DAP) and immunosuppressants can help improve muscle strength and function. Additionally, treating any associated malignancy is crucial for long-term management of the syndrome.