OBJECTIVETo detect the GJB2 gene mutation in patients with autosomal-recessive deafness, and analyze the relationship between clinical phenotype and gene mutation.

METHODSForty-two patients were examined clinically by pure tone audiometry, acoustic impedance and auditory brainstem response. The complete coding region of the GJB2 gene was amplified by polymerase chain reaction (PCR) and the PCR products were subjected to automatic DNA sequencing.

RESULTSTwo cases had homozygous mutation of 235delC. One of them had sensorineural hearing loss while the other had mixed hearing loss. Heterozygous mutation of 176del16bp was detected in a pair of twins who had mixed hearing loss. The 109G to A, 79G to A and 341A to G mutations were observed in both the patients and the controls.

CONCLUSIONHomozygous 235delC mutation is one of the pathogeni c mutations which could occur in patients with mixed hearing loss. The heterozygous 176del16bp mutation combined with environmental factor may cause hearing loss. The 109G to A, 79G to A and 341A to G variants were considered to be polymorphisms of the GJB2 gene.