ABU DHABI // In the mid-1990s scientists reported that members of a Bedouin family in the UAE had a rare genetic condition called Desbuquois syndrome.
A disorder of bones and cartilage, it affects growth to the extent that those with the condition may only be as tall as a toddler even when they have reached their late teens. Causing severe joint problems, it makes walking difficult.
Desbuquois syndrome is extremely rare, and the scientific paper was thought to be the first to report its presence in a Bedouin family.
One factor that may have caused its appearance in the family was marriage between close relatives. More prevalent in the Arab world, such marriages can lead to a variety of genetic conditions such as chronic blood disorders and malformations at birth.
The incidence in Arab countries of such illnesses, both rare and not so rare, can easily be found by using the online resources of the Centre for Arab Genomic Studies (Cags), which is part of the Sheikh Hamdan Award for Medical Sciences.
It is a decade since this Dubai organisation began to create a Catalogue for Transmission Genetics in Arabs (CTGA), part of what it describes as the biggest effort yet to define Arabs’ genetic disorders.
More than 1,500 conditions are included in the index, the initials of which are also the initials of the four nitrogen-containing “base pairs” – cytosine, thymine, guanine and adenine – that form the genetic code of DNA.
Anyone in need of a description of the symptoms of a disease, the genetics behind it and where it has been recorded, can find it easily.
The Cags’ efforts are poised to reach a milestone this year, as officials hope to complete a genetic map of the GCC. Saudi Arabia is the only part of the genetic jigsaw yet to be fitted in place.
Genetic maps are especially valuable in the Arab world because of the regional prevalence of congenital [present at birth] abnormalities and other problems caused by genes.
According to a 2006 scientific paper, Genetic Disorders in the Arab World, they cause a “major proportion” of the region’s cases of infant mortality and disability, while also leading to chronic blood and metabolic ailments.
Many abnormalities are caused by harmful recessive genes, as these exert their effects more commonly after marriages between close relatives, such as first cousins.
“In our part of the world, [consanguineous marriages] are maybe encouraged because of the social aspect of marrying somebody within the family,” said Dr Laila Zahed, a geneticist at the department of biomedical sciences at University of Balamand in Lebanon, who has been a Cags council member.
Typically, when a person is a carrier for a particular condition, they has an aberrant recessive form of a gene inherited from a parent, but this is masked by the presence of a normal, dominant version of the same gene from the other parent.
If a man and woman are related, such as first cousins, their children are more likely to inherit the same form of any particular gene from both parents, hence recessive disorders show up more frequently.
Aside from its burden of genetic disease, what also characterises the region, because of its large size, is how much people vary genetically from one area to another.
“You’re talking about people from North Africa, the Arabian Peninsula and the Mediterranean. The Arab world is really, really heterogeneous,” said Dr Zahed.
“[It’s because of] the history and the people who have travelled through … and the width of the region they come from.”
Therefore it is preferable for genetic maps to be as detailed as possible, because many genetic abnormalities are only present in what scientists describe as “sub-populations”, or sections of the population in a particular area, or in even smaller groups.
“In Palestine, there are some inherited issues that tend to segregate [to be separated during the production of reproductive cells and transmitted] even in certain families, but they don’t segregate in the population at large,” said Prof Moien Kanaan, a molecular geneticist at Bethlehem University and a Cags council member.
Detailed information of the kind Cags provides can therefore be of great help to doctors and clinical geneticists, making it easier for them to know which abnormalities to screen, according to Dr Zahed.
“If you have a patient, you won’t look for every mutation. It would be an advantage if someone has already looked at the mutations in, for example, Lebanon. It helps a lot and allows people to screen patients,” she said.
This information can be used to help identify cases where couples are at risk of having particular conditions. Genetic screening can take place even as early as when a man and woman are considering marrying, and such steps are actually compulsory in certain parts of the GCC for certain conditions.
Later on, tests during pregnancy can also determine, before a child is born, whether he or she will have a particular ailment.
“When you know the [variants of] genes present in the population, it’s easier to identify causative genes. Once you identify causative genes in families, you can offer them services like prenatal diagnosis, which will prevent occurrences, so the genetic burden will be reduced in the population,” said Prof Lihadh Al Gazali, a professor in clinical genetics at UAE University in Al Ain and a Cags executive board member.
According to Prof Al Gazali, who was one of the scientists who described Desbuquois syndrome in the Bedouin community, although various forms of screening are well-established in the Middle East, the region remains “relatively behind” some other parts of the world when it comes to clinical and scientific understanding of some genetic conditions.
She attributed that to the lack of clinical facilities and trained medical professionals.
It is hoped, therefore, that efforts such as those of Cags will help the region and advance its efforts to reduce the difficulties posed by genetically determined medical conditions.
“It’s very important [work]. The centre is not only for the UAE, they are studying the whole Arab world. It’s useful for clinicians like myself,” said Prof Al Gazali.
newsdesk@thenational.ae
