Conflict of interest: none.
Two is better than one: A case of homozygous myotonic dystrophy type 1
Article first published online: 22 MAY 2013
Copyright © 2013 Wiley Periodicals, Inc.
American Journal of Medical Genetics Part A
Volume 161, Issue 7, pages 1763–1767, July 2013
How to Cite
2013. Two is better than one: A case of homozygous myotonic dystrophy type 1. Am J Med Genet Part A 161A:1763–1767., , , , , .
- Issue published online: 19 JUN 2013
- Article first published online: 22 MAY 2013
- Manuscript Accepted: 14 MAR 2013
- Manuscript Received: 20 NOV 2012
- myotonic dystrophy;
- congenital myotonic dystrophy;
- trinucleotide repeat expansion;
Myotonic dystrophy type 1 is an autosomal dominant condition caused by a trinucleotide CTG repeat expansion in the 3′ untranslated region of the dystrophia myotonica protein kinase gene. The phenotypic features of myopathic facies, generalized weakness, and myotonia are thought to be dependent on repeat number, with larger expansions generally leading to earlier and/or more severe disease. The vast majority of individuals are heterozygous for an expanded allele and an allele in the normal range. In this clinical report, we describe two brothers with congenital myotonic dystrophy type 1. The younger of the two siblings is one of only 13 homozygous patients ever reported in the literature. He carries two expanded alleles: one with 1,170 repeats and the other with >100 repeats. We present his clinical picture in relation to his more severely affected heterozygous brother as well as other published homozygous cases. Finally, we discuss the inconsistency between repeat size and symptomatic expression as it applies to the current proposed mechanisms of myotonic dystrophy type 1 pathogenicity. © 2013 Wiley Periodicals, Inc.