Mouse anti-Human DMPK monoclonal antibody, clone 3G8

Dystrophia myotonica (DM) type 1 is an autosomal dominant disorder, caused by a trinucleotide CTG repeat expansion in the 3' untranslated region of the dystrophia myotonica protein kinase (DMPK) gene (chromosome 19q13.3). The disorder affects different organ systems, including the skeletal muscles, ocular lens, lungs, heart and gastrointestinal tract, as well as the endocrine and central nervous systems. The skeletal muscles are most frequently involved, whereby the disorder manifests as myotonia, muscle weakness and amyotrophy. However, DM type 1 presenting with dysarthria is rare. The current study presents a case of a 28-year-old male with DM type 1 presenting with dysarthria and associated multifocal hyperintense lesions in the white matter. Although electromyogram measurements identified myotonic discharges in all extremities, a muscle biopsy failed to detect the characteristic pathological features of DM type 1. A lack of a positive family history for DM type 1 also obscured diagnosis. However, genetic analysis detected a single allele in the P12 segment of the DMPK gene that included a CTG expansion of 13 repeats and a three-base gradient fragment in the P134 segment that included a CTG expansion of > 600 repeats. According to the characteristics of dysarthria, multifocal hyperintense lesions in the white matter, electromyogram measurement results and genetic testing results, a diagnosis of DM type 1 was confirmed.

Instability and expansion of the DMPK CTG repeat cause myotonic dystrophy type 1 (DM1), the most common adult-onset neuromuscular disorder. Overlapping clinical features between DM1 and other myotonic disorders necessitate molecular confirmation for definitive diagnosis. Preconception screening could improve reproductive planning especially in DM1-affected women, who show diminished ovarian reserve and unfavorable in vitro fertilization-preimplantation genetic diagnosis outcome. We optimized triplet-primed PCR and melting curve analysis on 17 DNAs from DM1-affected/unaffected cell Lines. A blinded test was performed on 60 genotype-known clinical samples. Plasmid constructs pDMPK(CTG)35 and pDMPK(CTG)48 were used to establish threshold temperatures separating DM1-affected from unaffected samples. Post-screen triplet-primed PCR amplicon sizing was achieved by short-cycle labeled-primer extension followed by capillary electrophoresis. Triplet-primed PCR melting curve analysis meLt peak temperatures of unaffected and DM1-affected samples were lower and higher than the control plasmids' melt peak temperatures, respectively. Capillary electrophoresis of post-melting curve analysis amplicons was completely concordant with the screening results. Triplet-primed PCR melting curve analysis is a simple and cost-effective screening tool for rapid identification of DM1. The companion confirmation protocol allows quick determination of CTG repeat size when required. This strategy avoids the need to perform capillary electrophoresis sizing on all test samples, Limiting capillary electrophoresis analysis to only a subset of cases that are screen-positive.