A Homozygous MYH1 Variant Underlies Autosomal Recessive Isolated Recurrent Rhabdomyolysis.

Rhabdomyolysis is a severe condition involving the breakdown of skeletal muscle fibers, leading to the release of muscle components into the bloodstream, which can lead to potential complications such as acute kidney injury and electrolyte imbalances. The etiology of rhabdomyolysis is multifactorial, encompassing traumatic, exertional, metabolic, infectious, toxic, and genetic causes. Genetic causes, including variants in LPIN1, RYR1, and CACNA1S, are increasingly recognized as significant contributors to recurrent rhabdomyolysis. MYH1 has recently been identified as a candidate gene for recurrent rhabdomyolysis with limited evidence originating from a single patient. In this report, we describe a 35-year-old male, born to consanguineous parents, who presented with recurrent rhabdomyolysis attacks, beginning at age 28, characterized by muscle pain, weakness, and episodes of acute kidney injury requiring dialysis. During attacks, the patient exhibited remarkably elevated markers of muscle breakdown and mildly elevated creatine kinase levels between episodes. A muscle biopsy revealed non-specific myopathic changes. Exome sequencing analysis was carried out and revealed a novel homozygous variant (NM_005963.4: c.1825G>A [p.Val609Met]) in MYH1 segregating in a manner compatible with an autosomal recessive pattern. In summary, this case provides confirmatory support for the role of pathogenic MYH1 variants in the pathogenesis of recurrent rhabdomyolysis and emphasizes the importance of comprehensive genetic testing in patients with unexplained recurrent episodes of muscle breakdown. Further cases are necessary to fully elucidate the genotypic and phenotypic spectrum of MYH1-related muscle disorders.