Mutations in the GJB2 gene are the most common cause of prelingual deafness, accounting for approximately half of all nonsyndromic recessive deafness. Among Japanese, the 233delC mutation, in which one cytosine (C) residue is deleted from a run of 3 Cs at necleotide position 233-235, with a carrier frequency of 1% is particularly common. The 233delC mutation is found in 50-70% Japanese patients with nonsyndromic recessive deafness. We have developed a genetic testing/technique that consists of Apa I and Bsp1286 I restriction analysis of polymerase chain reaction (PCR)-amplified 371 base pair DNA fragment of GJB2 gene, to identify this common mutation. This test provides a quick and reliable screening method for the common 233delC mutation. Genetic testing should be added to audiometric screening to identify children with prelingual deafness.
