Keeping it in the family: consanguineous marriage and genetic disorders, from Islamabad to Bradford

Courtesy: Dr. Lutf ur Rehman, Nashville, TN

Source: BMJ

Marrying close family members is a tradition in many countries and among their emigrants, leading to higher rates of genetic disorders. Reporting from Islamabad, Martina Merten asks how these disorders can be reduced

One billion people worldwide live in countries where marriage among relatives is common. Of this billion, one in three is married to a second cousin or closer relative or is the progeny of such a marriage.12 The frequency of genetic disorders among such children is around twice that in children of non-related parents.12

In some South Asian, Middle Eastern, and north African countries, as many as half of marriages are consanguineous.1 In Pakistan, half of the population marry a first or second cousin, more than in any other country.3 In rural areas this can be 80%, says Hafeez ur Rehman, an anthropologist at the Quaid-i-Azam University in Islamabad. Emigrants from these regions sometimes maintain these traditions.

The custom in all of these countries is similar, he told The BMJ, as marrying within the immediate family guarantees that wealth stays in the family. Partners will have similar socioeconomic status and similar family customs. A good relationship may already exist among parents in law. And divorce rates are believed to be lower.

Hafeez adds, “In our culture, marrying for love is still not highly looked upon, even if younger, educated people increasingly choose that path.”

According to the Pakistan Demographic and Health Survey in 2012-13, the probability of marriage for love increases with the woman’s level of education. But education remains an exception: only 36% of women and 46% of men in Pakistan attend secondary school.4

Genetic disorders are twice as likely

Children of consanguineous marriages are twice as likely to have genetic disorders as the 2-3% rate among children of non-related couples, says Salman Kirmani, professor of paediatrics at the Aga Khan University in Karachi and one of the few doctors in Pakistan to have specialised in genetics.

Common genetic disorders seen in children of consanguineous marriages include thalassaemias, cystic fibrosis, Down’s syndrome, infantile cerebral palsy, and hearing and visual disabilities,5 says Nabia Tariq, head of the department of gynaecology at the private Shifa College of Medicine in Islamabad.

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