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GENATLAS PHENOTYPE

last update : 05/05/07

Symbol	CHRND
Location	2q33-q34
Name	congenital myasthenic syndrome, type II
Corresponding gene	CHRND
Main clinical features	severe slow-channel (or fast-channel), D postsynaptic form, onset in infancy, with progressive weakness, athrogryposis in any cases, and impaired neuromuscular transmission without over degeneration of the motor endplate
Genetic determination	not applicable
Function/system disorder
Type	disease

Mechanism(s)

Gene mutation	Chromosome rearrangement	Effect	Comments
missense			mutation causes delayed opening of the channel, a finding that readily explains the marked congenital weakness in the absence of endplate degeneration

Remark(s)

P250Q mutation caused a decreased amplitude of the miniature endplate potential and current (MEPP and MEPC, respectively) to approximately 26 to 35% of normal mutation impairing co-clustering of the acetylcholine receptor with rapsyn

Genotype/Phenotype correlations

delta E59K causes dysfunction of fetal as well as the adult AChR and would explain the presence of joint contractures on the basis of reduced fetal movement