Novel single base pair COX III subunit deletion of mitochondrial DNA associated with rhabdomyolysis

Abstract A high number of cytochrome c oxidase (COX)-negative muscle fibres (approximately 45%) without ragged red fibres was found in a 27-year-old male patient with a single unprovoked episode of severe rhabdomyolysis. There was no family history of neuromuscular disorder and sequencing revealed a novel COX III single base pair deletion (MT-CO3{ NC_012920.1 }:m.[9559delC]). The deletion creates a frame shift and downstream termination codon affecting the last 136 amino acids (MT-CO3{YP_003024032.1}:p.[Pro118GlnfsX124]). The heteroplasmic mutation load in muscle was approximately 58% and single COX-negative fibres harboured significantly greater levels of mutant mitochondrial DNA than COX-positive fibres.