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

Background: 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. Results: 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 in...