By Syed Akbar
Hyderabad: Children born of close relation wedlock are known to suffer from a variety of genetic disorders and a fresh study by a team of city doctors and geneticists shows that they are highly prone to congenital deafness too.
A joint study by the Institute of Genetics and Hospital for Genetic Diseases and the ENT department of Osmania General Hospital reveals that children born out of consanguineous marriages are two times more susceptible to congenital deafness than ordinary children. The study was conducted in Government ENT Hospital and in various schools for the deaf in and around Hyderabad. The subjects ranged from neonates to children up to 14 years of age.
Dr PP Reddy of the Institute of Genetics told this correspondent that
among various causes for deafness, consanguinity is an established high risk etiological factor.
"The results showed that 41.73 per cent of the cases were the products of consanguineous matings and 58.27 per cent were born to non-consanguineous parents. Further analysis revealed a high rate of consanguinity (44.53 per cent) in children with non syndromic deafness. The percentage of consanguineous marriages in Andhra Pradesh is 22.36 but the rate of deafness in children born out of such wedlock is 41.73 per cent," he pointed out.
He said hearing impairment had debilitating effects on children as it could retard individual's language acquisition skills and impair the overall development. It is rapidly increasing sensory deficit among human beings and accounts for one third of the entire disease burden in the world.
The world-wide prevalence of profound, congenital deafness is 11 per 10,000
children, and is attributable to genetic causes in at least 50 per cent of the cases. The survey indicated that one out of every 1000 children born in India showed profound hearing loss.
Dr Reddy said the siblings of consanguineous marriages have a significantly higher incidence of autosomal recessive diseases including hearing impairment. Marriages within the family increase the risk of hearing impairment and other diseases.
"The development of cochlea and hair cells is dependent on a genetic pathway called Planar Cell Polarity pathway. This pathway is involved in the formation of the polarised structure of the auditory sensory organ and
regulates the embryonic development. Genetic aberrations caused due to consanguinity disturb the pathway leading to congenital hearing loss," he said.
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