BACKGROUNDThe mutation frequencies of three common deafness genes (MT-RNR1 m.1555A>G, GJB2, and SLC26A4) among patients with nonsyndromic sensorineural hearing loss (NSHL) were different in previous studies. Inconsistent selection criteria for recruiting patients could have led to differences in estimating the frequencies of genetic mutations thus resulting in different mutation frequencies among these studies. The aim of this study was to reveal the differences in the mutation spectrums of the three common genes between familial and sporadic Chinese Han patients.

METHODSTotally, 301 familial probands and 703 sporadic patients with NSHL were enrolled in this study. Three genes, MT-RNR1 m.1555A>G, GJB2, and SLC26A4, were screened for mutation in our study cohort. A χ(2) test was performed to compare the mutation frequencies between the two groups.

RESULTSThe study showed that the disease-causing mutation frequencies of MT-RNR1 m.1555A>G, GJB2, and SLC26A4 were 12.29%, 14.62%, and 18.27% in familial probands and 3.56%, 18.63%, and 18.92% in sporadic patients, respectively. The mutation frequency of MT-RNR1 m.1555A>G in familial probands was significantly higher than in sporadic patients (χ(2) test, P = 0.000), while there were no significant differences in the mutation frequencies of GJB2 and SLC26A4 between the familial and sporadic groups (χ(2) test, P > 0.05).

CONCLUSIONSIt is necessary to reveal the differences in gene mutation frequencies between patients of different sources or characteristics by comparative studies in order to avoid selection bias. The mutations of GJB2, SLC26A4, and MT-RNR1 m.1555A>G are the most important etiological factors in Chinese Han patients, among which SLC26A4 might be the most frequent.