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November 1993

The Myotonic Dystrophy Gene

Author Affiliations

From the Institute for Molecular Genetics (Drs Pizzuti and Caskey) and the Department of Medicine (Dr Friedman), Baylor College of Medicine, Houston, Tex, and the Howard Hughes Medical Institute, Baylor College of Medicine (Dr Caskey).

Arch Neurol. 1993;50(11):1173-1179. doi:10.1001/archneur.1993.00540110053005

The myotonic dystrophy gene codes for a protein kinase and contains a repeated trinucleotide motif (adenine-guanine-cytosine [AGC]) in its transcribed sequence. The repeat is polymorphic in the general population, varying in size from five to 37 AGC units in normal alleles. Myotonic dystrophy patients show expansions of the repeated sequence from over 50 elements up to several thousand units. There is a positive correlation between repeat size and clinical severity. The direct analysis of the AGC repeat size allows an easy confirmation of the clinical diagnosis of myotonic dystrophy in difficult cases and for prenatal counseling.

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