Genetic Testing for Consanguineous Marriages: Reducing Risks of Hereditary Diseases

Consanguineous marriages, or unions between closely related individuals, are common in certain cultures and regions, particularly in the Middle East and parts of South Asia. This tradition, while culturally significant, has notable implications for the prevalence of genetic disorders, including non syndromic hearing loss (NSHL), cystic fibrosis, thalassemia, and congenital disabilities.

Genetic Implications of Consanguineous Marriages

Consanguineous marriages are associated with an increased risk of autosomal recessive genetic disorders. This is because relatives are more likely to carry the same recessive genes inherited from a common ancestor. When both parents carry a copy of the same recessive gene, there is a higher chance that their children will inherit the condition.

For Instance , this study highlights the high prevalence of hearing loss in consanguineous families. In Pakistan, the rate of profound bilateral hearing loss is 1.6 per 1000, with 70% of these cases occurring in consanguineous families. Similarly, in India, regions with high rates of consanguineous marriages, such as Tamil Nadu (47%) and Maharashtra (25%), show a higher incidence of genetic disorders, including hearing loss. 

Genetic Testing for Early Identification

Genetic testing plays a crucial role in mitigating the risks associated with consanguineous marriages. 

1. Accurate Genetic Counseling:

The study introduces a protocol using Whole Exome Sequencing (WES) to screen consanguineous couples for pathogenic variants linked to autosomal recessive diseases. By sequencing the exomes of 39 couples, the researchers identified shared pathogenic or likely pathogenic variants in 53.8% of the cases, allowing for informed reproductive choices such as prenatal or preimplantation genetic diagnosis. The results suggest WES is an effective tool for genetic counseling in consanguineous couples, though limitations exist due to the current scope of known genetic variants.

2. Population-Based Screening:

Population-based screening has been proposed as a major strategy to translate genetic and genomic advances into population health gains. Identifying carrier couples through population screening could lead to a decrease in the incidence of certain autosomal recessive diseases in offspring. This could have a significant public health impact, particularly in areas with high rates of consanguinity.

Conclusion

The high prevalence of consanguineous marriages in the Middle East and South Asia necessitates the implementation of genetic testing as a preventive measure. By identifying carriers and providing accurate genetic counseling, genetic testing can significantly reduce the incidence of hereditary hearing loss and improve the overall health outcomes for future generations. As such, genetic testing is not just a tool for diagnosis but a crucial component of public health strategy in regions with high rates of consanguineous marriages. 

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