Dystrophinopathy mimicking metabolic myopathies

Recurrent rhabdomyolysis warrants comprehensive evaluations to search for underlying muscle diseases, including metabolic myopathies, LPIN1-myopathy, RYR1-myopathy, and less commonly muscular dystrophies. The absence of weakness and the normal or minimally elevated creatine kinase levels between attacks are typical of metabolic myopathies, LPIN1-myopathy, and RYR1-myopathy, while the presence of weakness and the highly elevated creatine kinase levels between attacks point toward muscular dystrophies. Here we report a 32-year-old man with a one-year history of recurrent rhabdomyolysis, who had normal strength, slightly elevated baseline creatine kinase level, and normal muscle histopathology. All workups for metabolic myopathies, LPIN1-myopathy and RYR1-myopathy were unrevealing. Next generation sequencing of muscular dystrophy-related genes revealed a hemizygous deletion of exons 17-34 of the dystrophin-encoding gene. Immunohistochemical study revealed absent staining for the rod domain of dystrophin. Dystrophinopathy should be considered in patients with recurrent rhabdomyolysis despite the absence of fixed weakness or highly elevated resting creatine kinase level.