CDH23 and hearing loss disorder: USH1D accounts for 19% to 35%4,5 of USH1 cases, and, as reported in a systematic metanalysis published in 2019, pathogenic variants in CDH23 were present in 6% (39/684) of patients with combined visual and hearing impairment due to USH, making it the third most common cause of dual sensory impairment (DSI) in affected individuals.6