OBJECTIVETo 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.

METHODSDNA 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.

RESULTSThe 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.

CONCLUSIONSThe 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.