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