Hereditary Hearing Loss and Consanguinity in Turkmen Population of Iran: A Retrospective Study

Background: Our research focuses on different dimensions of families of Turkmen population of Iran with two or more than two affected members. A complete clinical ear test was conducted on them. It was aimed to find families with the highest chance of hereditary hearing impairment among siblings and also existence of consanguinity among their parents. Materials and Methods All Turkmen families with at least two hearing impaired members were screened based on prenatal and postnatal histories, family medical history, socioeconomic status as well as physical examination. For confirmation of hereditary hearing loss, a comprehensive evaluation including prenatal, perinatal and postnatal history, family medical history, pattern of inheritance, consanguinity, and three generation pedigree, the physical examination, and genetic screening by a genetic expert were used. They were referred for complete hearing evaluation including pure tone audiometry, speech recognition threshold, otoacoustic emission and auditory brainstem response. Results A total of 82 families with 198 hearing impaired patients were diagnosed with about 60% having two and the rest with more than two affected members. Nearly 89% (n=175) of the patients had the inherited type of hearing loss among which 95% (n=167) demonstrated non-syndromic symptoms. The rate of consanguinity among parents of the patients was about 65%. Conclusion This research revealed a high incidence of hereditary hearing impairment and consanguinity among Turkmen population which is in agreement with other reports from Iranian population with deaf children. In general, the rate of consanguinity in Iranian population is 38%. Therefore, it seems that consanguinity is higher in families with hearing-impaired children.