Phenotype-genotype analysis of the autosomal recessive hereditary hearing loss caused by OTOA variations / 中华耳鼻咽喉头颈外科杂志

Objective: To analyze the phenotypic-genotypic characteristics of hereditary deafness caused by OTOA gene variations. Methods: Family histories, clinical phenotypes and gene variations of six pedigrees were analyzed, which were diagnosed with hearing loss caused by OTOA gene variations at the PLA General Hospital from September 2015 to January 2022. The sequence variations were verified by Sanger sequencing and the copy number variations were validated by multiplex ligation-dependent probe amplification (MLPA) in the family members. Results: The hearing loss phenotype caused by OTOA variations ranged from mild to moderate in the low frequencies, and from moderate to severe in the high frequencies in the probands, which came from six sporadic pedigrees, among which a proband was diagnosed as congenital deafness and five were diagnosed as postlingual deafness. One proband carried homozygous variations and five probands carried compound heterozygous variations in OTOA gene. Nine pathogenic variations (six copy number variations, two deletion variations and one missense variation) and two variations with uncertain significance in OTOA were identified in total, including six copy number variations and five single nucleotide variants, and three of the five single nucleotide variants were firstly reported [c.1265G>T(p.Gly422Val),c.1534delG(p.Ala513Leufs*11) and c.3292C>T(p.Gln1098fs*)]. Conclusions: OTOA gene variations can lead to autosomal recessive nonsyndromic hearing loss. In this study, the hearing loss caused by OTOA defects mostly presents as bilateral, symmetrical, and postlingual, and that of a few presents as congenital. The pathogenic variations of OTOA gene are mainly copy number variations followed by deletion variations and missense variations.

Prenatal genetic test and clinical guidance for 213 hereditary deaf families / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To summarize the workflow, strategy and experience of prenatal genetic test for deafness based on the 6-year clinical practice.</p><p><b>METHODS</b>There were 213 families who received prenatal test from 2005 to 2011. Among the 213 families, 205 families had had one deaf child, including 204 couples with normal hearing and one couple of the deaf husband and normal wife, 8 families including 6 couples with normal hearing and 2 deaf couples, had no child before test. Genomic and mitochondrial DNA of each subject was extracted from whole blood. The etiology and recurrent risks in 212 families were confirmed by means of the genetic test of GJB2, SLC26A4 and mtDNA 12sRNA, but one family carried POU3F4 c.647G > A heterozygous mutation causing X-linked hereditary hearing impairment confirmed by pedigree study. The prenatal test was carried out during the pregnancy of all mothers from 11 to 30 weeks, and the following genetic information and counseling were supplied based on the results.</p><p><b>RESULTS</b>The recurrent risk was 25% in 209 families, including 204 families with one deaf child and 5 families without child, among which all couples were GJB2 or SLC26A4 mutation carriers and deaf children were caused by homozygous or compound GJB2/SLC26A4 mutations; The recurrent risk was 50% in 3 families, the father and his child in one family had compound SLC26A4 mutations and the mother with heterozygous SLC26A4 mutation, the wife had POU3F4 c.647G > A heterozygous mutation in another one family, and the husband with compound SLC26A4 mutations and the wife with mtDNA A1555G mutation and heterozygous SLC26A4 mutation simultaneously happened in the rest one family; The recurrent risk was 100% in one family of the deaf couple who were both found to carry homozygous or compound GJB2 mutations, and the deaf wife got pregnant by artificial insemination with the sperm from the local Human Sperm Bank. 226 times of prenatal test were applied in all 213 families that 11 families of them received prenatal test twice, and one family received three times. 46 times of prenatal testing showed that the fetuses carried parental mutations simultaneously or the same mutations with probands; while 180 times of prenatal test showed that the fetuses carried only one parental mutation or did not carry any mutation from parents. The following visit showed that all of these 180 families had given birth to babies who were all revealed to have normal hearing by new born hearing screening test.</p><p><b>CONCLUSIONS</b>Prenatal diagnosis for deafness assisted by genetic test can provide efficient information about offspring's hearing condition, and the normative workflow and precise strategy highly guarantee the safe and favorable implementation of prenatal diagnosis.</p>

Prenatal genetic counseling and instruction for deaf families by genetic test / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>Analyzed the molecular pathogenesis of probands by means of genetic test and assisted the local Family Planning Institute by providing prenatal genetic counseling and instruction for deaf families who eager to have more baby.</p><p><b>METHODS</b>Total of forty-three deaf families were recruited by two institutes for family planning from Guangzhou and Weifang. Forty-two families had one deaf child with normal hearing parents. One family was that parents and their child were all deaf. Genetic testing of GJB2, SLC26A4 and mitochondrial DNA (mtDNA) 12SrRNA were firstly performed in probands and their parents, following medical history, physical examination, auditory test and CT scan of temporal bone were completed. And then the genetic information and instruction were provided to each deaf family.</p><p><b>RESULTS</b>Fifteen of these 43 families had positive results of genetic test. In fifteen families, one family was confirmed that the parents and their child all carried homozygous GJB2 mutations and the recurrence risk was 100%. Twelve families were confirmed that the probands carried homozygous/compound GJB2 or SLC26A4 mutations while their parents were GJB2 or SLC26A4 carriers, and the recurrence risk was 25%. One family was confirmed that the proband, diagnosed with enlarged vestibular aqueduct syndrome (EVAS) by CT scan, carried heterozygous SLC26A4 mutation from the mother, and the recurrence risk was still 25% based on the hereditary pattern of EVAS although another SLC26A4 mutation from the father was not found. One family was confirmed that the proband carried a heterozygous GJB2 mutation from the mother and the possibility to be GJB2 carrier for offsprings was 50%. The rest 28 families were that all probands and their parents did not carry GJB2, SLC26A4 and mtDNA 12SrRNA pathological mutation.</p><p><b>CONCLUSIONS</b>Genetic testing can provide more accurate and useful prenatal genetic counseling and instruction to deaf families. Meanwhile, it is an ideal way to develop a cooperative relationship with the institute for family planning.</p>

Etiologic analysis of severe to profound hearing loss patients from Chifeng city in Inner Mongolia / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To investigate the etiology of patients with severe to profound hearing loss and to identify the ratio of hereditary hearing loss in Chifeng area in Northern China.</p><p><b>METHODS</b>DNA were extracted from peripheral blood of 134 deaf patients from Chifeng special educational school and 100 normal hearing controls in Northern China. Audiology examinations showed that all patients had severe to profound bilateral sensorineural hearing impairment. Sequence analysis of the whole coding areas of GJB2, GJB3, GJB6, SLC26A4, mtDNA12SrRNA and mtDNAtRNASer(UCN) were performed. Individuals carrying SLC26A4 mutation were given further temporal bone CT scan.</p><p><b>RESULTS</b>The ratio of hearing loss related to genetic factors in this population was 60.45% (81/134). About 33.58% (45/134) of the patients were given accurate genetic diagnosis. GJB2 mutations were responsible for approximately 17.16% of the cases in ChiFeng area. By screening SLC26A4 followed by temporal bone CT scan, we diagnosed 20 cases of enlarged vestibular aqueduct (EVA) and/or other inner ear malformation. SLC26A4 mutations account for about 14.93% of the cases. The aminoglycoside-related mtDNA 1555A>G mutation accounted for 0.76% of the cases in Chifeng area. In addition, another 13.43% (18/134) of the cases carried heterozygous GJB2 mutation and their hearing loss may be related to GJB2. 6.72% (9/134) of the cases carried heterozygous SLC26A4 mutation who were not found EVA by temporal bone CT or not took CT examination for some reasons. However, their hearing loss may also be SLC26A4-related. About 2.24% (3/134) of the cases carried mtDNA 12SrRNA 1095 T>C which may also be an aminoglycoside-related mutation and very likely be the cause of hearing loss. GJB3 might participate in the pathomechanism of hearing loss in 1.49% (2/134) of the patients. GJB6 mutation was not detected in this population.</p><p><b>CONCLUSIONS</b>The ratio of hearing loss related to genetic factors in the sample drawing population from Chifeng was 60.45% (81 cases). GJB2 is the most common gene and SLC26A4 is the second common gene next to GJB2 that cause deafness in this area.</p>

Phenotype and genotype analysis of a Chinese family with prelingual X-linked hereditary hearing impairment / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>X-linked hearing impairment is clinically and genetically a heterogeneous disease. Although many disorders manifest with hearing loss, a limited number of sex-linked loci and only one gene (POU3F4) have been shown to be implicated in X-linked non-syndromic hearing impairment. In the present study, we have performed a clinical and genetic analysis of a Chinese family with X-linked non-syndromic hearing loss, with emphasis on audiological findings and genomic mapping.</p><p><b>METHODS</b>The clinical features of Family JX01 were evaluated by physical and audiometric examination in eighteen family members. Mutation screening of POU3F4 was identified by polymerase chain reaction (PCR) amplification and sequencing. Molecular evaluation consisted of X-chromosome wide genotyping by microsatellite makers (STR), followed by analyzing using MLINK computer program.</p><p><b>RESULTS</b>Five affected males demonstrated bilateral, symmetrical sensorineural and profound hearing loss. The hearing impairment started prelingual. The female carriers did not have any complain of hearing loss, however, two of them were tested with milder loss with high frequency. No causative mutations in POU3F4 gene were detected by DNA sequencing. Linkage analysis indicated that the responsible gene was linked to locus DXS1227 (maximum lod score = 2.04 at theta = 0).</p><p><b>CONCLUSIONS</b>The affected males in Family JX01 have profound prelingual sensorineural hearing impairment. In addition, two female carriers showed mild to moderate hearing losses. However, none of females complained of any hearing loss. Analysis of hereditary deafness in this family mapped most compatibly to the Xq27.2.</p>

Sequencing analysis of whole SLC26A4 gene related to IVS7-2A > G mutation in 1552 moderate to profound sensorineural hearing loss patients in China / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To investigate the whole sequence of SLC26A4 gene among 1552 deaf students from 21 regions of China with SLC26A4 hot spot mutation IVS7-2A > G and analyze the epidemiological state of enlarged-vestibular-aqueduct-syndrome (EVAS) related hearing loss in China.</p><p><b>METHODS</b>DNA was extracted from peripheral blood of 1552 students from deaf and dumb school of 21 regions in China. The nationality of the 1552 cases covers Han (1290 cases), Uigur (69 cases), Hui (37 cases), Mongolia (31 cases), Yi, Zhuang, Bai, Miao and other 13 nationalities (125 cases). Firstly, all subjects were analyzed for the hot spot mutation IVS7-2A > G by direct sequencing. Those carrying a single heterozygous IVS7-2A > G were given further analyzed for the probable second mutation in other exons except exon7 and exon8 of SLC26A4. One hundred and fifty cases with normal hearing were in the control group.</p><p><b>RESULTS</b>The sequencing results revealed 197 cases carrying IVS7-2A > G, of whom 83 carrying IVS7-2A > G homozygous mutation, 114 carrying IVS7-2A > G heterozygous mutation. Of the 114 cases with heterozygous IVS7-2A > G, 78 cases were found to have another mutation and 36 cases were found no other mutation in SLC26A4. Of the 1552 cases, the percentage of cases carrying homozygous IVS7-2A > G and compound heterozygous mutations was 10.37% (161/1552). Of the 78 cases with SLC26A4 compound heterozygous mutations, the mutations except IVS7-2A > G were found mainly in exon 19, 10, 17, 15, 11 + 12, 14 and 3. Twenty-one novel SLC26A4 mutations were found. In the control group, there were only 3 cases carrying heterozygous IVS7-2A > G, and no other mutation in SLC26A4 was found.</p><p><b>CONCLUSIONS</b>SLC26A4 mutations account for at least 10% of EVAS related hereditary hearing loss in China. It's of great importance to screen SLC26A4 gene for making aetiological diagnosis for deafness. The discovery of novel variants of SLC26A4 gene makes the mutational and polymorphic spectrum more plentiful in Chinese population. We also provide preliminary evidence for the hot spot areas of SLC26A4.</p>

Nonsense mutations in the PAX3 gene cause Waardenburg syndrome type I in two Chinese patients / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Waardenburg syndrome type I (WS1) is an autosomal dominant disorder characterized by sensorineural hearing loss, pigmental abnormalities of the eye, hair and skin, and dystopia canthorum. The gene mainly responsible for WS1 is PAX3 which is involved in melanocytic development and survival. Mutations of PAX3 have been reported in familiar or sporadic patients with WS1 in several populations of the world except Chinese. In order to explore the genetic background of Chinese WS1 patients, a mutation screening of PAX3 gene was carried out in four WS1 pedigrees.</p><p><b>METHODS</b>A questionnaire survey and comprehensive clinical examination were conducted in four Chinese pedigrees of WS1. Genomic DNA from each patient and their family members was extracted and exons of PAX3 were amplified by PCR. PCR fragments were ethanol-purified and sequenced in both directions on an ABI_Prism 3100 DNA sequencer with the BigDye Terminator Cycle Sequencing Ready Reaction Kit. The sequences were obtained and aligned to the wild type sequence of PAX3 with the GeneTool program.</p><p><b>RESULTS</b>Two nonsense PAX3 mutations have been found in the study population. One is heterozygous for a novel nonsense mutation S209X. The other is heterozygous for a previously reported mutation in European population R223X. Both mutations create stop codons leading to truncation of the PAX3 protein.</p><p><b>CONCLUSIONS</b>This is the first demonstration of PAX3 mutations in Chinese WS1 patients and one of the few examples of an identical mutation of PAX3 occurred in different populations.</p>

Features of nationwide distribution and frequency of a common gap junction beta-2 gene mutation in China / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To determine the prevalence of a common GJB2 mutation in a big Chinese population of deaf children and the features of its distribution in regions all over the nation and to provide epidemiology data and expertise for genetic testing of deafness in China.</p><p><b>METHODS</b>The DNA samples of NSHI patients and normal controls were collected from different typical areas of China. The method of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) with ApaI was used to determine the genotype of GJB2 235 site.</p><p><b>RESULTS</b>Totally 16.3% of patients carried at least one 235 delC mutant allele. Among them, 7.8% was homozygous and 8.5% was heterozygous. The prevalence of GJB2 235delC mutation in China was evident, and the significant difference of 235delC mutation frequency was found in sub-population from different areas and different ethnic groups.</p><p><b>CONCLUSIONS</b>Based upon the result of this screening as stated, Chinese NSHI patients appear to have 235delC frequency and the number of GJB2 related deafness was estimated to be huge. The testing of GJB2 235delC mutation would play an important role in genetic diagnosis and screening in China. As high as 15% of patients could be diagnosed as GJB2 caused deafness (bi-allelic mutation) only by means of this simple, fast and economic assay. In addition, patients were negative for 235delC mutation would be candidates for further mutational analysis of GJB2 or other deafness related genes.</p>

Frequency of SLC26A4 IVS7-2A > G mutation in patients with severe to profound hearing loss from different area and ethnic group in China / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To carry out molecular epidemiology study of SLC26A4 IVS7-2 A > G mutation in large Chinese deaf population and to provide evidence for fast screening and gene diagnosis of enlarged vestibular aqueduct syndrome (EVAS).</p><p><b>METHODS</b>A total of 1979 patients with non-syndromic hearing loss(NSHL) underwent questionnaire and PCR for IVSA > G mutation detection of SLC26A4 gene.</p><p><b>RESULTS</b>All 245 patients (12.38%) with homozygotes and heterozygotes IVS7-2 A > G mutation were found among the 1979 NSHL It showed statistically significant difference among north and northeast, northwest, east and southeast, southwest and central area in China. (chi2 = 34.4899, P < 0.05). Carrier frequency of the central area (27.52%) was notably higher than southwest area (6.69%). The IVS7-2 A > G mutation was most frequently found in Han deaf groups (13.88%). Tibetan, Hui, and other western minorities were lower than Han deaf population (chi2 = 35.4456, P < 0.05).</p><p><b>CONCLUSIONS</b>A high SLC26A4 IVS7-2 A > G mutation frequency for deafness in Chinese patients was found. Detection of the pathogenic mutations was bringing the possibility to detect EVAS at an early stage. Moreover, it might help to establish diverse diagnostic strategies toward differently ethical deaf population in different region of China.</p>

Genetic counseling and instruction for deaf couples directed by genetic testing / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To analyze the molecular pathogenesis of deaf couples by means of genetic testing. To provide accurate genetic counseling and instruction for deaf couples with different etiology based upon results of genetic testing.</p><p><b>METHODS</b>Four deaf families from July 2005 to May 2006. Each subject was with moderate to profound hearing loss. Genomic and mitochondrial DNA (mtDNA) of each subject were extracted from whole blood. Genetic testing of GJB2, SLC26A4 (PDS) and mtDNA A1555G mutation were offered to each individuals.</p><p><b>RESULTS</b>The husband from family 1 didn't carry GJB2, SLC26A4 and mtDNA A1555G mutation while his wife was confirmed to carry compound SLC26A4 mutations. The possibility of their offspring's to be SLC26A4 single mutation carrier was 100%. The couple from family 2 both didn't carry GJB2, SLC26A4 and mtDNA A1555G mutation. The possibility of their offspring's having hereditary deafness caused by GJB2, SLC26A4 and mtDNA A1555G mutation was excluded. The husband from family 3 was confirmed to carry homozygous GJB2 mutations and a single SLC26A4 mutation while his wife who was diagnosed with enlarged vestibular aqueduct syndrome (EVAS) by CT scan was proven to carry a single SLC26A4 mutation. The risk of their offspring's suffering EVAS was 50%. The husband from family 4 was mtDNA A1555G positive while his wife who was diagnosed with cochlear malformation by CT scan didn't carry GJB2, SLC26A4 and mtDNA A1555G mutation. The risk of their offspring's having hereditary deafness caused by GJB2, SLC26A4 and mtDNA A1555G mutation was excluded.</p><p><b>CONCLUSIONS</b>Genetic testing could be applied to offer the more accurate genetic counseling and instruction to deaf couples.</p>

Audiological and vestibular evaluation of new coagulation factor C homology mutation carriers in a Chinese family / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To analyze the clinical features of audiological and vestibular function in a Chinese family with late onset autosomal dominant nonsyndromic sensorineural hearing loss.</p><p><b>METHODS</b>Comprehensive audiological and vestibular evaluation including pure tone audiometry, auditory brainstem response (ABR), electrocochleogram (EcochG), oculomotor testing, caloric tests, rotational testing, computerized dynamic posturography and vestibular evoked myogenic potentials (VEMP) were conducted to identify the hearing and vestibular impairment.</p><p><b>RESULTS</b>All affected family members shared sensorineural hearing loss with full penetrance starting between the second and fifth decade of life as a high frequency loss which progresses to a severe to profound loss at the sixth to seventh decade. The extensive vestibular evaluation indicated that all affected members performed normally in computerized dynamic posturography and caloric testing. Impairment of the saccular otolith in all of six affected members was suggested by results of the VEMP test. The velocity step test generated abnormal time constants and sinusoidal oscillation test generated abnormal gains and phase in affected members indicated that horizontal canal vestibular hyporeflexia in history. All affected subjects examined in this family showed completely normal ocular motor responses in oculomotor testing, including smooth pursuit, optokinetic nystagmus, gaze and saccade.</p><p><b>CONCLUSIONS</b>The predominant feature of the Chinese DFNA9 family was that all the affected subjects harboring COCH mutation in the vWFA2 domain didn't suffer the vestibular symptoms during their life time and comprehensive vestibular assessment revealed only subtle vestibular hypofunction in affected members of this family. There is a genotype-phenotype correlation in DFNA9.</p>

Prenatal diagnosis for hereditary deaf families assisted by genetic testing / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To provide prenatal diagnosis for deaf families, which the first child was confirmed to be hereditary deafness caused by gap junction beta-2 (GJB2) or SLC26A4 (PDS) mutation, to avoid another deaf birth in these families.</p><p><b>METHODS</b>Eight deaf families joined in this study. Each family had one child with severe to profound hearing loss while parents had normal hearing except a deaf father from family 8; mothers had been pregnant for 6-28 weeks. Genetic testing of GJB2, SLC26A4 and mitochondrial DNA (mtDNA) A1555G mutation were firstly performed in probands and their parents whose DNA was extracted from peripheral blood, and then prenatal testing was carried out in the fetus whose DNA was extracted from different fetus materials depending on the time of gestation.</p><p><b>RESULTS</b>The probands from family 1-4 were found to carry homozygous or compound GJB2 mutations while their parents carried corresponding heterozygous GJB2 mutations. The probands from family 5-8 and the deaf father from family 8 were found to carry compound SLC26A4 mutations while their parents and the mother from family 8 carried a single SLC26A4 mutation. Prenatal testing showed that the fetuses from family 1, 5, 8 only carried the paternal mutation and the fetuses from family 2, 3, 6 didn't carry any GJB2 or SLC26A4 mutations. The new born babies from these six families all had normal hearing revealed by new born hearing screening. However, the fetuses from family 4,7 carried the same mutations with probands in each family. The parents from family 4, 7 decide to terminate pregnancy.</p><p><b>CONCLUSION</b>Prenatal diagnosis assisted by genetic testing can provide efficient information about hearing condition of their offsprings.</p>

Patients suffered from enlarged vestibular aqueduct syndrome in Chifeng deaf and dumb school detected by Pendred's syndrome gene hot spot mutation screening / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To investigate the incidence of hot spot mutation of PDS gene by genetic screening testing method in Chifeng City, Inner Mongolia. The feasibility and effectiveness of genetic screening method in finding enlarged vestibular aqueduct syndrome were confirmed by temporal bone CT scan.</p><p><b>METHODS</b>DNA were extracted from peripheral blood of 141 students of Chifeng Deaf and Dumb school. PDS IVS7-2 A-G mutation, the most common PDS mutation in Chinese population, was analyzed by direct sequencing for PDS exon 7, exon 8 with intron 7. The individuals found with homozygous or heterozygous PDS IVS7-2 A-G mutation were given further temporal CT scan, ultrasound scan of thyroid and thyroid hormone assays. The results of PDS genetic screening and temporal bone CT scan were compared with each other.</p><p><b>RESULTS</b>The sequencing results revealed twenty cases carrying PDS IVS7-2 A-G mutation, of whom nine cases were homozygous mutation and eleven cases were heterozygous mutation. Eighteen cases underwent temporal bone CT scan except two cases that left the school due to other health problem. Sixteen cases were confirmed to be enlarged vestibular aqueduct syndrome (EVAS) by CT scan and the shape and function of thyroid were clinically normal by ultrasound scan of thyroid and thyroid hormone assays, respectively.</p><p><b>CONCLUSIONS</b>The patients suffered from EVAS can be diagnosed by the screening for the PDS hot spot mutation which has unique advantage in epidemiologic study in large scale deaf population. The preliminary data of this study suggested relatively high incidence of EVAS in Chifeng area.</p>

Diagnostic methods and clinic application for mtDNA A1555G and GJB2 and SLC26A4 genes in deaf patients / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To establish the method of clinic genetic testing for common deaf genes such as mtDNA nt1555, GJB2 gene and SLC26A4 (Pendrin's syndrome gene, PDS) gene.</p><p><b>METHODS</b>Three hundred and sixty seven sporadic patients with hearing loss from out-patient department of General Hospital of Chinese People's Liberation Army, 60 patients with history of maternal inherited hearing loss from 27 family, 20 congenital deaf patients from special educational school for deaf and dumb, 3 deaf patients with enlarged vestibular aqueduct (EVA) confirmed by CT scan, 50 control individuals with normal bone conductive hearing were analyzed. The genetic testing kit for mtDNA A1555G mutation was used to detect mtDNA A1555G mutation. The whole gene sequencing were accomplished in 20 congenital deaf patients. In 3 patients with EVA, fragments covering all exons of PDS gene were analyzed by denatured high productive liquid chromatogram and special exons were sequenced when DHPLC showed abnormal wave patterns of amplicons covering these exons.</p><p><b>RESULTS</b>Fifty nine patients from 26 family and 5 sporadic patients were found to carry mtDNA A1555G mutation. Among 20 congenital deaf patients, 2 cases were found to have homozygous GJB2 235 del C mutation, 1 case had compound 235del C and 299-300 del AT mutation. Other 2 cases carried heterozygous 109 A-G mutation. Among 3 patients with EVA, 1 case was found to have heterozygous PDS G316X mutation and other 2 cases had homozygous 919-2 A-G mutation. CONCLUSIONS Genetic testing for deafness is feasible procedure with remarkable clinic significance.</p>