Lambert-Eaton myasthenic syndrome (LEMS) is a rare condition in which the immune system attacks the neuromuscular junctions – the areas where your nerves and muscles connect. Normally, the nerve cells send signals to muscle cells to help muscles move. When the neuromuscular junctions are attacked, this interferes with the ability of nerve cells to send signals to muscle cells resulting in muscle weakness especially of the muscles in the legs and arms. Over time, the muscle weakness becomes worse leading to reduced physical activity and fatigue.
The disease may affect a patient’s ability to walk or do daily activities. Onset is often gradual with weakness increasing over time and other muscles such as muscles of the shoulders, hands, feet, speech, swallowing and eyes being affected later. Of note, a little over half of patients with LEMS also have a certain type of cancer called small cell lung cancer.