HypothesisThe purpose of this study was to elucidate whetherGJB2mutations are responsible for childhood deafness in Southeast Asia.BackgroundGJB2mutations are responsible for a large part of childhood deafness in many countries. In Whites, there is a common mutation (35delG) that accounts for about 70 to 80% of theGJB2mutations. Previously, we and others reported a commonGJB2mutation (235delC) in Japanese patients with prelingual deafness. The association of the 235delC mutation with a single haplotype suggested a founder effect of the mutation.MethodsWe analyzed theGJB2gene in 17 deaf patients from 12 unrelated families in Thailand. Genomic DNA was extracted from peripheral lymphocytes of each patient and the entire coding region of theGJB2gene was sequenced.ResultsGJB2mutations were found in 4 patients in 3 families. Patient 1 was a homozygote of 235delC. Patient 2 was a compound heterozygote of 235delC and W24X (71G → A). Patient 3A and 3B (in 1 family) were heterozygotes of a novel mutation M34L (100A → T).ConclusionThe 235delC mutation may be widely distributed in Asian countries outside of Japan.