Congenital Myasthenic Syndrome With Episodic Apnea in Patients Homozygous for a CHAT Missense Mutation
Simone Kraner;
Iris Laufenberg;
Hans M. Straßburg, MD;
Joern P. Sieb, MD;
Ortrud K. Steinlein, MD
Arch Neurol. 2003;60:761-763.
Background The syndrome of congenital myasthenia with episodic apnea (CMS-EA) was previously found to be due to mutations in the choline acetyltransferase gene (CHAT).
Objective To identify the mutations underlying CMS-EA in a Turkish multiplex family.
Design Direct sequencing of the CHAT gene.
Patients A consanguineous Turkish family with 2 siblings affected by muscular weakness and episodic respiratory distress.
Results The sequencing of CHAT coding exons identified a previously unknown missense mutation that affected a highly conserved amino acid residue (I336T). The mutation was absent in 164 control chromosomes.
Conclusions The high degree of conservation in different species strongly suggests that I336T is a functionally important amino acid residue. The absence of I336T from a large control sample further supports the pathogenic role of I336T in CMS-EA. This is the second report of CHAT mutations causing presynaptic CMS.
From the Institute of Human Genetics, University Hospital, Rheinische-Friedrich-Wilhelms University of Bonn, Bonn (Mss Kraner and Laufenberg, and Dr Steinlein); Department of Pediatrics, Bavarian-Ludwig-Maximilians University of Würzburg, Würzburg (Dr Straßburg); and the Department of Neurology, Max Planck Institute of Psychiatry, Munich (Dr Sieb), Germany.
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