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Myotonic dystrophy type 2: molecular, diagnostic and clinical spectrum
J W Day1, K Ricker, J F Jacobsen
1Institute of Human Genetics, Department of Neurology, University of Minnesota School of Medicine, Minneapolis, MN 55455, USA. johnday@umn.edu
Neurology
|February 26, 2003
Summary
Myotonic dystrophy type 2 (DM2) is a dominantly inherited disorder caused by CCTG repeat expansions. A new assay improves detection, revealing clinical similarities to DM1 but lacking a congenital form.
Area of Science:
- Genetics
- Molecular Biology
- Neurology
Background:
- Myotonic dystrophy types 1 (DM1) and 2 (DM2/PROMM) are inherited disorders with multisystemic features.
- DM2/PROMM is caused by a CCTG repeat expansion in the ZNF9 gene.
Purpose of the Study:
- Characterize the clinical and molecular features of DM2/PROMM.
- Improve molecular detection rates for DM2/PROMM.
Main Methods:
- Genetic and clinical evaluation of 379 individuals from 133 DM2/PROMM families.
- Comparison of clinical and molecular features in 234 individuals.
- Development of a novel repeat assay for molecular detection.
Main Results:
- Common DM2 symptoms include myotonia (90%), weakness (82%), cataracts (61%), diabetes (23%), and cardiac involvement (19%).
- A new assay increased molecular detection from 80% to 99%.
- Affected offspring showed shorter repeat expansions than affected parents.
Conclusions:
- DM2, prevalent in northern European populations, clinically resembles adult-onset DM1.
- Key differences include the absence of a congenital form in DM2.
- Shared multisystemic features in DM1 and DM2 are attributed to RNA-level effects of CUG/CCUG expansions.
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