Lambert Eaton Myasthenic Syndrome (LEMS): An Autoimmune Syndrome Causing Muscle Weakness Lambert Eaton Myasthenic Syndrome belongs to the class of disorders referred to as neuromuscular transmission disorders. That is to say, that this group of diseases affects the ability of the nerves to communicate with the muscles and thus leads to muscle weakness. Lambert Eaton Myasthenic Syndrome (LEMS) is also an autoimmune disorder because it is a product of the body that is acting to cause the disorder. In other words, the body is acting against itself to cause disease. Finally, LEMS is often a paraneoplastic disorder. The term paraneoplastic refers to a disease that is indirectly caused by a neoplasm or cancer. While we will discuss LEMS in detail, it is important to know that a variety of paraneoplastic syndromes exist and can be the first signs of a malignancy. PATHOPHYSIOLOGY In order to understand LEMS, it is necessary to first understand how muscles are made to work. We will ta