Specificities of the DMD Point Variant Spectrum in Russian Patients With Duchenne/Becker Muscular Dystrophy

Duchenne/Becker muscular dystrophy (DMD/BMD) is a severe progressive form of muscular dystrophy which manifests in boys at the age of 1-8 years. The disorder is mainly characterized by proximal muscle weakness, which leads to impaired movement and subsequently total disability. DMD/BMD is caused by pathogenic variants in the DMD gene, which lead to a deficit in the production of various dystrophin isoforms. Seeing as the disorder was characterized many years ago, the DMD mutation spectrum has been described by multiple authors around the world. The most common variants are gross deletions and duplications of one or multiple exons, comprising 55%-65% and 6%-11% of all variants in this gene respectively. Other DMD/BMD cases (20%-30%) are caused by point variants. The current study describes the full spectrum of point variants in the DMD gene among Russian patients, analyzing the variant distribution in the gene and establishing the repeating variants in the examined cohort. Such comprehensive analysis is essential for genetic counseling and disorder prognosis, as well as determining the suitable therapeutic approach in each particular case.