Paraneoplastic disorders affecting the neuromuscular junction or anterior horn cell

Paraneoplastic neurologic disorders can affect any part of the nervous system. Rarely, the motor neuron or motor axons may be affected in patients with cancer, leading to clinical signs and symptoms that resemble ALS. Myasthenia gravis (MG) is the prototypic autoimmune disorder of the nervous system. In most cases, MG is an idiopathic disorder, and the events leading to the production of acetylcholine receptor autoantibodies are not known. About 15% of patients have a paraneoplastic form of MG associated with a thymic neoplasm (thymoma). Patients with paraneoplastic MG typically have late-onset generalized MG and require long-term immunosuppression. Another form of neuromuscular junction disorder, the Lambert-Eaton myasthenic syndrome, often occurs as a paraneoplastic manifestation of small cell lung cancer. Together, MG and Lambert-Eaton syndrome are the most common paraneoplastic neurologic disorders.