A case of Becker muscular dystrophy in a woman with skewed X-chromosome inactivation

The article presents a rare case of Becker muscular dystrophy symptoms development in a female patient manifested by weakness in the muscles of the lower limbs in youth. The diagnosis was established based on clinical symptoms, molecular-genetic testing, electromyography data, magnetic resonance imaging of the lower limb muscles, and blood creatine phosphokinase activity. DNA analysis using the next-generation sequencing «Large neurological panel» (Genomed laboratory, Moscow) yielded data supporting the presence of a deletion of the X chromosome segment with approximate boundaries 31323344-32809866 and a size of 1.486.522 bp, encompassing regions of the OMIM-annotated <i>DMD</i> gene. Multiplex ligation-dependent probe amplification (MLPA) using commercial kits SALSA MLPA Probemix P034-DMDI and P035-DMD2 (MRC-Holland) was performed to search for deletions/duplications of exons 1-79 of the DMD gene. As a result of the analysis, a deletion of exons 7-62 of the DMD gene in a heterozygous state was identified. Thus, the presence of the deletion was confirmed by the reference method. DNA analysis was conducted to detect skewed X-chromosome inactivation. The results show an 87%:13% ratio, indicating skewed (non-random) X-chromosome inactivation (repeats count 24/26).