Myasthenia gravis

In myasthenia gravis, fatigability and persistent, often fatal weakness of voluntary muscles are attributable to dysfunction at the neuromuscular junction. The overall dysimmune state of the patient probably causes the junctional defect. 70% of patients have thymic hyperplasia and 10%, thymoma. The atrophy of muscle fibers usually looks like denervation atrophy, and there are morphologic abnormalities of motor axon endings and the postsynaptic region of the muscle fiber. Electromyographic studies detect the neuromuscular junction defects: fatigue on repetitive stimulation and post tetanic exhaustion. 'Open biopsy EMG' confirms that the commonly found electromyographic pattern comes from regions showing only denervation like atrophy of muscle fibers. Other diagnostic tests include benefit from anticholinesterases and worsening by d tubocurarine; the worsening of weakness by lactate infusion might serve as a diagnostic test. Treatment includes anticholinesterases, thymectomy, and the recently introduced long term, high single dose, alternate day prednisone program. Experienced 24 hr nursing surveillance is essential to treatment of the severely myasthenic patient.