Rare biallelic variants in PCDH12 (OMIM 605622) and PCDH15 (OMIM 605514) have been reported in patients with diencephalic–mesencephalic junction dysplasia syndrome 1 (DMJDS1; OMIM 251280), Usher syndrome type 1F (USH1F, OMIM 602083), and nonsyndromic hearing loss (DFNB23; OMIM 609533), respectively [24, 25]. The gene discussed is PCDH15; the disease is autosomal recessive nonsyndromic hearing loss 23.