Myasthenia gravis: clinical features, pathogenesis, evaluation, and medical management.

Myasthenia gravis is a disorder characterized by weakness and fatigue of voluntary muscles. The muscular disorder is generalized in 85% and confined to extraocular muscles in 15% of patients. The disease is graded based on pattern and severity of muscular involvement. Myasthenia gravis is an autoimmune disease which leads to a reduction of the number of acetylcholine receptors (Ach-R) at the muscular motor endplate. This results in less receptors available for stimulation, lower amplitude stimulations, less muscle fiber activation, and the resultant clinical findings of weakness in the affected muscles. The work-up and treatment of this disease originated from an understanding of its pathogenesis. Diagnostic tests include use of anticholinesterase agents (tensilon test), curare test, repetitive nerve stimulation, Ach-R antibody assay, and single fiber electromyography. Medical therapy includes use of anticholinesterase agents, immunotherapy, and plasmapheresis.