PRPS1 and hearing loss disorder: It has been reported that other genetic disorders caused by phosphoribosylpyrophosphate synthetase 1 (PRPS1) mutations, which causes hyperuricemia due to overproduction of purine, are accompanied by sensorineural hearing loss (34, 35); however, we could not perform whole exome sequencing in the present case to investigate the possibility that KCS2 overlaps with such other genetic disorders.