Genetic disorders afflict Arab world

Birth defects throughout the Arab world are closely linked to marriages between relatives.

Abu Dhabi // The growing prevalence of genetic disorders throughout the Arab world will place greater financial strain on health systems and public health infrastructure across the region, a Dubai-based research centre has warned. The Centre for Arab Genomic Studies (CAGS) yesterday said Arab countries were showing greater prevalence of many hereditary disorders caused both by environmental and social dynamics, but that diagnoses were often made too late.

Since beginning work in 2004, the centre has collected extensive data from the UAE, Bahrain and Oman, identifying more than 450 genetic disorders in the population sample. Disorders such as Down's syndrome, sickle cell disease, and thalassaemia are far more common in the region than elsewhere. Many genetic conditions that are considered rare are found more frequently in the region. According to CAGS, 21.4 babies per 100,000 are born with Down's in the UAE, about double the average global rate.

The direct cost to treat just one carrier of thalassaemia, a recessive blood disease, is about US$6,000 (Dh22,000) a year. About one in 10 people in the UAE is a carrier, CAGS said. Saudi Arabia has the highest rate of birth defects in the Gulf, with around 80 babies out of every 1,000 born with a disorder. In the UAE, Kuwait and Oman, 70 to 79 children in every 1,000 are born with a birth defect.

Sudan has the highest rate in the world at 82 per 1,000, while France has the world's lowest rate, at 39 per 1,000. Birth defects have been closely linked to marriages between cousins and relatives, a common practice throughout the region and estimated to account for 35 to 50 per cent of all weddings. Such traditions can increase the number of carriers of recessive genes, leading to higher rates of birth defects. Selective and environmental factors, including a lack of public awareness about how to prevent such conditions, also compound the problem.

Autosomal recessive disorders, in which two copies of the gene must mutate for a person to be affected, form an overwhelming proportion of genetic disorders in Arab patients in the UAE, according to CAGS, which says high rates of marriage between relatives are a leading contributor to the condition. An affected person usually has unaffected parents who both carry a mutated gene. Up to half of all Emirati marriages are between relatives, with 54 per cent of married couples in Al Ain being relatives, compared to 32 per cent in Abu Dhabi and 40 per cent in Dubai.

Saudi Arabia, has perhaps the highest rate of intermarriage, with up to two thirds of all marriages occurring between relatives. There are no national projects aimed at controlling genetic disorders in most Arab countries, said Dr Ghazi Tadmouri, the assistant director of CAGS. Prenatal, and even "pre-implantation" detection of diseases should be more available, he said, while early diagnosis is essential to treating many disorders that increase rates of neonatal death and mortality in both children and adults. "Before implantation we can take one of the cells, we make a diagnosis, if the diagnosis is positive for a genetic defect that sample will not be implanted. This will save the worry of abortion and all related issues," Dr Tadmouri said. The King Faisal Specialist Hospital in Saudi Arabia is the only place in the Arab world that offers a "pre-implantation screening" for prospective parents, and has performed the service for around 70 couples. Other preventive measures include screening potential partners before marriage to see if they are both carriers of a particular recessive gene. "Now it is becoming mandatory to do basic screening for thalassaemia and other diseases before marriage," Dr Tadmouri said. "Of course no one would oblige partners to not marry if they were both carriers of a disease." There are other factors that make some diseases more prolific in the area, Dr Tadmouri said. Thalassaemia is prevalent in areas with high malaria rates because one of the side effects of being a carrier of the genetic trait is a natural protection against the disease. "However, if you go into the details of some of these diseases you will always find them described as occurring in certain families or tribes, or confined to certain geographical regions. In that case consanguinity is one main reason for that disease to be occurring." [e-mail]