Background/Objectives: Rhabdomyolysis is a potentially life-threatening condition characterized by acute skeletal muscle breakdown. In addition to well-described external triggers, a genetic contribution is increasingly recognized. We aimed to (I) review the genetic diagnostic approach of rhabdomyolysis, (II) evaluate the clinical characteristics indicative of a genetic susceptibility with the ‘RHABDO’ acronym, and (III) assess the predictive value of the presence RHABDO features for identifying genetic variants. Methods: In this retrospective two-center study, 122 patients underwent genetic testing for rhabdomyolysis since the introduction of whole exome sequencing (WES) in 2013. The presence of RHABDO features was compared between those with (likely) pathogenic variants and those with benign or no identified variants or variants of uncertain significance. Results: The testing methods included panel-based WES (82%), Sanger sequencing (49%), and full WES (24%), of which 52 patients (43%) underwent multiple methods. A (likely) pathogenic variant was identified in 13 patients (11%), in all of whom ≥2 RHABDO features were present. The positive predictive value for ≥2 features was 14%, while the negative predictive value was 100%. Conclusions: These results highlight the relevance of WES in further elucidating the genetic basis of rhabdomyolysis and demonstrated that RHABDO is a valuable tool for selecting patients who should undergo genetic testing.

Brody disease is a rare autosomal recessive myopathy, caused by pathogenic variants in the ATP2A1 gene. It is characterized by an exercise-induced delay in muscle relaxation, often reported as muscle stiffness. Children may manifest with an abnormal gait and difficulty running. Delayed relaxation is commonly undetected, resulting in a long diagnostic delay. Almost all published cases so far were adults with childhood onset and adult diagnosis. With diagnostic next-generation sequencing, an increasing number of patients are diagnosed in childhood. We describe the clinical and genetic features of 9 children from 6 families with Brody disease. All presented with exercise-induced delayed relaxation, reported as difficulty running and performing sports. Muscle strength and mass was normal, and several children even had an athletic appearance. However, the walking and running patterns were abnormal. The diagnostic delay ranged between 2 and 7 years. Uniformly, a wide range of other disorders were considered before genetic testing was performed, revealing pathogenic genetic variants in ATP2A1. To conclude, this case series is expected to improve clinical recognition and timely diagnosis of Brody disease in children. We propose that ATP2A1 should be added to gene panels for congenital myopathies, developmental and movement disorders, and muscle channelopathies.