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Genet Test Mol Biomarkers. 2015 Dec;19(12):703-9. doi: 10.1089/gtmb.2015.0135. Epub 2015 Oct 27.

Development and Validation of a New Molecular Diagnostic Assay for Detection of Myotonic Dystrophy Type 2.

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1 Research Laboratories-Molecular Biology, IRCCS Policlinico San Donato , Milan, Italy .
2 Service of Laboratory Medicine, IRCCS Policlinico San Donato , Milan, Italy .
3 Laboratory of Muscle Histopathology and Molecular Biology, IRCCS Policlinico San Donato , Milan, Italy .
4 Department of Biomedical Sciences for Health, University of Milan , IRCCS-Policlinico San Donato, Milan, Italy .
5 Neurorehabilitation Unit, University of Milan , NEMO Clinical Center (NeuroMuscular Omnicomprehensive), Fondazione Serena, Milan, Italy .



Myotonic dystrophy (DM) is the most common adult form of muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia, and multiorgan involvement. Myotonic dystrophy type 2 (DM2) is caused by a [CCTG] expansion in the ZNF9/CNBP gene. The aim of this work was the validation of the new molecular diagnostic test Myotonic Dystrophy type 2 kit-FL.


A cohort of 126 individuals was analyzed. The results show that 126/126 patients were correctly identified using the new molecular assay. In particular, 74 were DM2 positive, 39 were DM2/DM1 negative and 13 DM2 negative/DM1 positive. Approximately 9.5% (7/74) of the DM2-positive samples had a single sizeable expansion and 85% (63/74) showed multiple bands or smears. Comparative fluorescence in situ hybridization (FISH) analyses, on muscle biopsies, revealed that the sensitivity and specificity were very high (>99%). Equivalent analytical performances were obtained using different DNA extraction methods. Among affected individuals 87.5% (28/32) had electrical myotonia, 69% (22/32) proximal weakness, 41% (13/32) cataracts, and about 37.5% (12/32) cardiac conduction defects. FISH analysis and clinical data were used to support the genetic analysis.

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