Objective   To detect the mutations of GJB2 and mtDNA A1555G in Chongqing children with hereditary hearing loss.    Methods   Totally 195 deaf children were included to identify their medical history of hearing loss

use of aminoglycosides

and other clinical abnormalities through filling a questionnaire by their parents

with 100 normal children as control. The audiological and neurological examinations of these children were conducted

including otoscopy

pure-tone audiometry

acoustic brainstem evoked response (ABR) and otoacoustic emission. GJB2 gene 235delC mutation and mtDNA A1555G mutation were detected with specific restriction enzyme digestion.    Results   Homozygous deletion C at position 233-235 of GJB2 (235delC) resulted in frameshift mutation. GJB2 gene mutations were found in 46 patients (23.58%) with hereditary hearing loss. The allelic frequency of 235delC allele was 18.44% in the hearing loss children and 2.00% in the control children (P0.01). Seven hearing loss children were found to carry mtDNAA1555G mutation.    Conclusion   The incidence of GJB2 gene and mtDNA A1555G mutations among the deaf-mute children in Chongqing is higher than the average level of overall Chinese deaf population. Molecular genetic screening for these mutations is effective method to prevent the occurrence of hereditary hearing loss.