Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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January 1, 2015
Myotonic Dystrophy (Steinert Disease)
- Myotonic muscular dystrophy type 1 (DM1), also known as Steinert disease, is the most common adult form of muscular dystrophy. It results from the expansion of a short (CTG) repeat in the DNA sequence of the DMPK (myotonic dystrophy protein kinase) gene (chromosome 19 or 3).
- Age: Classic DM1, typically 20s and 30s (less commonly after age 40 years). It is a disorder characterized by progressive muscle weakness, wasting, and occasionally cognitive decline.
- Key Diagnostic Features
- MRI demonstrates mild cerebral cortical atrophy, subcortical white matter lesions (WML), and ventricular dilatation.
- The subcortical WML are frequently found in the frontal and parietal lobes.
- Anterior temporal lobe involvement represents a characteristic feature in DM1.
- The severity of subcortical white matter involvement correlates with cognitive dysfunction.
- Molecular genetic testing, muscle biopsy, and electromyography are confirmatory.
- DDx:
- CADASIL
- HIV dementia
- Posterior reversible encephalopathy syndrome
- Radiation-induced change
- Toxic-metabolic disorders
- Rx: Symptomatic