Myasthenia gravis: pathogenesis, diagnosis, and therapy.

: Myasthenia gravis most commonly affects the ocular muscles. Abnormal fatigability of the involved muscle groups is the most remarkable feature of the physical examination. Recent studies have demonstrated that a thymus-derived antibody plays a role in the pathogenesis of myasthenia gravis, which is now thought to be an autoimmune disorder. Its association with other autoimmune disorders has been recognized for some time. A high index of suspicion is the most essential element in diagnosis. Rapid and reproducible response to administration of anticholinesterase leaves little doubt of the diagnosis, but characteristic EMG findings in myasthenic muscle evoked by repetitive stimulation of peripheral motor nerve are definitive. Anticholinesterase drugs are the mainstay of therapy. Thymectomy is indicated in patients with thymoma and in some young persons with serious disease. Patients who respond poorly to anticholinesterase therapy or surgery are candidates for steroid therapy.