The Clinical investigator
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The Clinical investigator · May 1994
Case ReportsMyotonic dystrophy and limb girdle muscular dystrophy in one family.
A family is reported in which a 29-year-old woman showed the clinical features of myotonic dystrophy while her 26-year-old brother presented with the clinical picture of limb girdle syndrome. In the affected female, direct genetic testing for the specific myotonic dystrophy mutation on chromosome 19 revealed abnormal expansion of a repeat unit containing the three nucleotides cytosine, thymine, and guanine (CTG)-typical for myotonic dystrophy-while her diseased brother displayed two normal alleles. ⋯ The number of CTG repeats in the diseased women was approximately tenfold higher than in her asymptomatic relatives who revealed an abnormal allelic pattern. The increase in CTG repeats with transmission to a subsequent generation in this family was paralleled by a dramatic increase in the severity of myotonic dystrophy.