title: Pathophysiology of weakness in a patient with congenital end-plate acetylcholinesterase deficiency.
abstract: A Japanese patient with congenital end-plate acetylcholinesterase (AChE) deficiency developed severe proximal and truncal muscle weakness with preservation of distal strength. Electrophysiological studies included a train of stimuli at 3 HZ, which induced a marked decremental response in the deltoid but not in the first dorsal interosseous (FDI) muscle. Single fiber electromyography (EMG) revealed a high blocking rate (23.1 +/- 30.5%, n = 13) with a markedly increased jitter (mean consecutive difference [MCD] 297 +/- 218 micros) in the deltoid, but a low blocking rate (6.2 +/- 7.4%, n = 16) despite an equally increased jitter (MCD 227 +/- 147 micros) in the FDI. In vitro microelectrode study and computer simulation suggested that the combination of a large jitter and a low blocking rate may be ascribed to a reduced end-plate potential (EPP) amplitude with an abnormally prolonged decay time constant (tau). These characteristics may constitute the primary underlying pathophysiologic mechanism in our patient and in similar cases of congenital myasthenic syndrome.
authors.affiliation: Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kohara
authors.forename: Thy-Sheng
authors.initials: TS
authors.lastname: Lin
authors.forename: Takayasu
authors.initials: T
authors.lastname: Fukudome
authors.forename: Jun
authors.initials: J
authors.lastname: Kimura
authors.forename: Takashi
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Ryuji
authors.initials: R
authors.lastname: Kaji
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shibasaki
mesh_terms: D000110:Acetylcholinesterase / Q000172:deficiency* / Q000235:genetics; D000328:Adult; D004576:Electromyography; D005260:Female; D006801:Humans; D009045:Motor Endplate / Q000201:enzymology / Q000503:physiopathology*; D009119:Muscle Contraction / Q000502:physiology; D018908:Muscle Weakness / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000503:physiopathology*; D020294:Myasthenic Syndromes, Congenital / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology*; D009431:Neural Conduction / Q000502:physiology; D010525:Peripheral Nerves / Q000503:physiopathology; D012815:Signal Processing, Computer-Assisted
chemical_list: D000110:Acetylcholinesterase