Coexistence of a CAV3 mutation and a DMD deletion in a family with complex muscular diseases

Whole-exome sequencing (WES) can comprehensively detect both pathogenic single nucleotide variants and copy number variants, enabling identification of a coexistence of two or more genetic etiologies. Here we report a family consisting of individuals with Becker muscular dystrophy and rippling muscle disease. The proband, a 12-year-old boy, was diagnosed with Becker muscular dystrophy with exon 45-55 DMD deletions at age 4. He had myalgia and muscle stiffness. Interestingly, percussion-induced muscle mounding (PIMM), which is a characteristic of rippling muscle disease, was also observed. The father also showed muscle stiffness, myalgia, fatigability, muscle rippling and PIMM. WES revealed a missense CAV3 mutation (NM_033337.2:c.80G>A) in the proband, the father, the oldest sister and the grandmother, who had an elevated serum creatine kinase (CK) level. The c.80G>A mutation was considered pathogenic according to ACMG guidelines. The second older sister, the mother and the paternal grandfather did not have the CAV3 mutation and had normal CK. Using two programs for copy number analysis with WES data, we successfully identified the DMD deletion in the proband, the older sister and the mother. We revealed the coexistence of the CAV3 mutation and the DMD deletion in a family with complex muscular diseases and confirmed the usefulness of WES for elucidating such etiology.