Myasthenia gravis, motor neuron syndrome and thymoma.

An adult male with thymomatous myasthenia gravis (MG) and a motor neuron syndrome simulating amyotrophic lateral sclerosis is reported. After thymectomy and corticosteroid therapy, the MG remitted. During 4 years of follow-up, the lower motor neuronsigns in the upper limbs and upper motor neuron signs in the lower limbs remained unchanged. Literature concerning paraneoplastic neurological syndromes associated with thymoma has been reviewed.