Consanguinity and Ocular Genetic Diseases in South India: Analysis of a Five-Year Study

Abstract

Objective: Consanguineous marriage is a widely practised social custom in Asia and northern Africa. In south India, Dravidian Hindus have contracted consanguineous marriages for over 2,000 years. In the present study, the influence of consanguinity on the prevalence of visual disorders was examined in patients attending a specialist genetic eye clinic. Subjects and Methods: A total of 2,335 patients attending Sankara Nethralaya, Chennai, India, were screened for genetic eye disorders over a five-year period. The patients were drawn from all parts of India and from neighbouring countries in south Asia. Results and Discussion: Six hundred and seventy-three (28.8%) of the patients tested for ophthalmic genetic disorders reported a family history of consanguinity. The majority (n = 574) of these families were from south India. In the patient group as a whole, the most common form of consanguineous union was between first cousins (n = 367), followed by uncle/niece marriage (n = 177), equivalent to a mean coefficient of inbreeding α = 0.0202. Among the consanguineous families, 430 of 673 (63.9%) had retinitis pigmentosa, 167 of these cases were autosomal recessive and 199 were isolated cases. The public in regions such as south India should be made aware of the merits and demerits of consanguineous marriages.

Primary Immunodeficiency Disorders in India—A Situational Review

“…There is a huge burden of consanguineous and endogamous marriages in India (25, 26). The figure varies from 1% in some states to as high as 38% in others.…”

Consanguinity, endogamy, and genetic disorders in Tunisia

“…Consanguineous marriages are also recognized as being associated with higher risk for autosomal recessive diseases than in the general population (Taillemite et al 1985;Alwan and Modell 1997;Kumaramanickavel et al 2002) by favoring the expression of recessive deleterious alleles. Many reports have highlighted a positive association between inbreeding and a number of recessive single gene disorders like achromatopsia (Tchen et al 1977), Leber's congenital amaurosis, xeroderma pigmentosum (Mokhtar et al 1998), and metabolic defects like aminoacidopathies and mucopolysaccharidoses (Jaouad et al 2009).…”

Paternal age and common mental disorders

“…Consanguinous marriages or marriages between biologically related or blood relatives have been reported to contribute to the inheritance of many genetic and congenital disorders (Kumaramanickavel et al 2002;Al-Ghazali et al 2006). This has been described when parents are of similar ancestry as seen in autosomal disorders like haemoglobinopathies, glucose-6-phosphate dehydrogenase, and ocular genetic disorders such as retinitis pigmentosa (Kumaramanickavel et al 2002;Al-Ghazali et al 2006). Practice of arranged marriages among relatives like cousins, uncles and nieces still occur in Asia where the man can be much older especially between uncles and nieces.…”