Dr. Bird has received licensing fees from Athena Diagnostics, Inc. Mission Hospitals' Fullerton Genetics Laboratory has provided in-kind support for analysis and interpretation of DNA sequence data for patients included in the study. Dr. Tarleton is an employee of this nonprofit institution. All remaining authors have nothing to disclose.
Truncating CLCN1 mutations in myotonia congenita: Variable patterns of inheritance
Article first published online: 20 SEP 2013
Copyright © 2013 Wiley Periodicals, Inc.
Muscle & Nerve
Volume 49, Issue 4, pages 593–600, April 2014
How to Cite
Richardson, R. C., Tarleton, J. C., Bird, T. D. and Gospe, S. M. (2014), Truncating CLCN1 mutations in myotonia congenita: Variable patterns of inheritance. Muscle Nerve, 49: 593–600. doi: 10.1002/mus.23976
- Issue published online: 17 MAR 2014
- Article first published online: 20 SEP 2013
- Accepted manuscript online: 28 JUL 2013 10:27PM EST
- Manuscript Accepted: 16 JUL 2013
- allelic variability;
- myotonia congenita
Introduction: Myotonia congenita due to protein truncating CLCN1 mutations is associated with variable patterns of inheritance. Methods: Three family kindreds are described, all of whom possess protein truncating mutations (Y33X, fs503X, R894X). One lineage also has coexistent R894X, A313T, and A320V mutations. Results: The Y33X mutation kinship has autosomal recessive inheritance and a severe phenotype when homozygous. The fs503X family has autosomal dominant inheritance and a moderate-to-severe phenotype. The A313T mutation kindred also has autosomal dominant inheritance but expresses a mild phenotype, except for the more severely affected compound heterozygotes. Conclusions: Early truncating mutations precluding dimerization are expected to be autosomal recessive and express a severe phenotype, while later mutations may be variable. The pedigrees presented here demonstrate that intrafamilial phenotypic variability may result from a dosage effect of an additional mutation, not necessarily variable expressivity. Mutations that have unexpected patterns of inheritance may represent allelic variability. Muscle Nerve 49:593–600, 2014