Congenital myasthenia: end-plate acetylcholine receptors and electrophysiology in five cases.
The nature of the defect in congenital myasthenia was investigated in biopsy specimens of intercostal muscle from 5 male patients whose symptoms presented between birth and 2 years of age. Miniature end-plate potentials were reduced in amplitude in all 5 patients. The number of acetylcholine receptors as determined by alpha-bungarotoxin binding was normal in case 1 and reduced in cases, 2, 4, and 5. The shape of the end-plates as shown by autoradiography and cholinesterase staining was normal in case 1 and elongated in cases 2, 4, and 5. In cases 3, alpha-bungarotoxin binding was slowly reversible, and there were some muscle fibers with multiple end-plate regions. The acetylcholine content of the muscle was normal in all 5 cases. None of the patients had serum antibody to human acetylcholine receptor as measured by immunoprecipitation or inhibition of alpha-bungarotoxin binding. We conclude that congenital myasthenia is a heterogeneous condition of nonimmune etiology in which both presynaptic and postsynaptic defects can be found.
D000109:Acetylcholine / Q000032:analysis; D000293:Adolescent; D000328:Adult; D002038:Bungarotoxins / Q000378:metabolism; D006680:HLA Antigens / Q000032:analysis; D006801:Humans; D008297:Male; D009045:Motor Endplate / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D009157:Myasthenia Gravis / Q000151:congenital / Q000503:physiopathology*; D009469:Neuromuscular Junction / Q000503:physiopathology*; D011950:Receptors, Cholinergic / Q000032:analysis* / Q000276:immunology
D002038:Bungarotoxins; D006680:HLA Antigens; D011950:Receptors, Cholinergic; D000109:Acetylcholine