Hereditary hearing loss and deafness genes in Japan.

Hearing loss (HL) is the most common sensory impairment occurring at birth in developed countries. Epidemiological data show that more than one child in 1000 is born with HL, while more than 50% of prelingual HL cases are found to be hereditary. Approximately 70% of hereditary HL is nonsyndromic and subdivided to autosomal dominant (20%), autosomal recessive (75%), X-linked HL (1%), and maternally-inherited HL associated with the mitochondrial DNA mutation. More than 10 deafness genes have been reported to be responsible for nonsyndromic hereditary HL in Japan. Among them, the most prevalent causative genes, GJB2 and the mitochondrial DNA 12SrRNA are introduced. In addition, this study also refers to the specific genes responsible for the unique audiogram, mainly WFS1. Finally, the genes related to the enlargement of vestibular aqueduct of inner ear abnormality, SLC26A4, EYA1 and SIX1 are discussed. The clinical and genetic findings associated with these disorders including the results of a recent study are reviewed.