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>

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>