A novel deep intronic mutation expands the genotype spectrum of MYH7-related myopathies

Congenital myopathies are a heterogeneous group of rare inherited muscle disorders. Despite the good sensitivity of whole-exome sequencing in detecting pathogenic variants, many cases remain molecularly unsolved. Here, we present the case of a woman with congenital myopathy that remained unsolved for many years, in which the application of whole-genome sequencing enabled the identification of a novel deep intronic mutation in the MYH7 gene. A 22-year-old woman developed muscle weakness since infancy, with frequent falls, toe-walking, and difficulty climbing stairs. Muscle biopsy revealed atrophy of type 1 fibers relative to type 2, consistent with fiber-type disproportion. After a long “molecular odyssey,” whole-genome sequencing performed on the patient–parents trio identified a de novo deep intronic variant in MYH7. This case further underscores the importance of pursuing the search for the causative gene to enable more accurate clinical monitoring and tailored health care.