Clinical Characteristics of Patients With Becker Muscular Dystrophy Having Pathogenic Microvariants or Duplications

Background and Objectives: cause progressive worsening of motor dysfunction, muscle weakness and atrophy, and death due to respiratory and cardiac failure. BMD often has in-frame deletions that preserve the amino acid reading frame, but there are some cases with microvariants or duplications. In recent years, the importance of therapeutic development and care for BMD has been emphasized. Therefore, the purpose of this study was to understand the clinical characteristics of BMD patients with microvariants or duplications and to determine the genotype-phenotype relationship. Methods: variants, muscle biopsy findings, skeletal muscle, respiratory and cardiac function, and CNS involvement were collected and analyzed statistically. Many patients with microvariants had abnormal ECG findings. The effect of variant type on patient outcomes varied. Regardless of the type of microvariant, skeletal muscle and respiratory dysfunction was more severe in mutants of the cysteine-rich/C-terminal domain than in rod domain mutants. On the other hand, there was no significant difference in the complication rate of CNS disorders among the 3 domains of dystrophin. Discussion: Microvariant forms, in particular, tend to vary in clinical severity according to the site of the dystrophin protein mutation rather than the type of pathogenic variant. The results of this study may be useful for genetic counseling, care, and treatment of patients with BMD.