PCDH15 and autosomal recessive nonsyndromic hearing loss 23: Mutations in CDH23 were found to cause Usher syndrome type 1D (USH1D) and nonsyndromic deafness DFNB12 [10,11], while mutations in PCDH15 were associated with Usher syndrome type 1F (USH1F) and nonsyndromic deafness DFNB23 [12].