Mutant alleles in PCDH15 may contribute to isolated forms of profound deafness (DFNB23, phenotype ID: 609533) and Usher syndrome subtype USH1F, characterized by congenital profound sensorineural hearing loss, progressive RP, and vestibular impairment. This evidence concerns the gene PCDH15 and autosomal recessive nonsyndromic hearing loss 23.