Genetic disorders in the Arab world

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Abstract
Why are genetic disorders common in the Arab world? Available data suggest that genetic and congenital disorders are more common in Arab countries than in industrialised countries; recessively inherited disorders account for a substantial proportion of physical and mental handicap.1–3 6 Several factors may contribute to the high prevalence of genetically determined disorders: High consanguinity rates—25-60% of all marriages are consanguineous, and the rate of first cousin marriages is high (figs 1 and 2; table A on bmj.com).4 w1 In addition, isolated subpopulations with a high level of inbreeding exist. Furthermore, in many parts of the Arab world the society is still tribal.5 6 w1 This has made the epidemiology of genetic disorders complicated, as many families and tribal groups are descended from a limited number of ancestors and some conditions are confined to specific villages, families, and tribal groups, leading to an unusual burden of genetic diseases in these communities (table B on bmj.com)1 2 5 The high prevalence of haemoglobinopathies, glucose-6-phosphate dehydrogenase deficiency, autosomal recessive syndromes, and several metabolic disorders (fig A and table C on bmj.com)1 2 5 The rate of children with Down's syndrome in some Arab countries exceeds the 1.2-1.7 per 1000 typical for industrialised countries. This may be related to the relatively high proportion of births to older mothers in the region (up to 50% of children with Down's syndrome in the region are estimated to be born to mothers aged 40 or over)1 2 7 w3 The lack of public health measures directed at the prevention of congenital and genetic disorders, with inadequate health care before and during pregnancy, particularly in low income countries2 Services for the prevention and control of genetic disorders are restricted by certain cultural, legal, and religious limitations, such as the cultural fear of families with genetic diseases being stigmatised within their community and the legal restrictions on selective termination of pregnancy of an affected fetus.1 2 5 6 View larger version: In this window In a new window Fig 1 Two Arab pedigrees showing high level of consanguinity, large family size, and several affected children in different sibships View larger version: In this window In a new window Fig 2 Average rates of marriages between first cousins among Arabs. UAE=United Arab Emirates Summary points The population in Arab countries is characterised by large family size, high maternal and paternal age, and a high level of inbreeding Genetic disorders are common in Arab countries and account for a substantial proportion of physical and mental handicap Generally, no public health measures are directed at the prevention of congenital and genetic disorders, which is also restricted by cultural and legal limitations Some countries have started cost effective prevention programmes for certain common genetic disorders, such as premarital carrier screening for haemoglobinopathies Strategies for the prevention of genetic disorders in this region should include integration of community genetics into the primary healthcare system, education, and strengthening the existing specialised genetic service Sources We collected information for this report from published literature through a Medline search, from experts working in medical genetics and providing genetic services, and from personal archives of references taken from locally published medical journals in Arab countries. The main documents that we used extensively as references include the World Health Organization Eastern Mediterranean Regional Office publication Community Control of Genetic and Congenital Disorders2 and the Oxford Monographs on Medical Genetics on Genetic Disorders among Arab Populations.1