A common mutation in the CBS gene explains a high incidence of homocystinuria in the Qatari population.
We report the results of a study carried out to delineate genetic and epidemiological aspects of homocystinuria in the Qatari population. Sixty-four patients with homocystinuria (37 males, 27 females, age 1 to 29 years) from 31 nuclear families were ascertained over a period of more than four years. The incidence of homocystinuria in Qatar was calculated to be > or =1:3000, the highest in the world known so far. All patients in whom data were available were vitamin B6-nonresponsive. Molecular studies were performed in all patients. All 53 patients from tribe M and all three patients from tribe K were homozygous for the mutation c.1006C>T (p.R336C) in the CBS gene, with an additional seven patients resulting from mixed marriages between tribe M and tribe K. A single patient from tribe S was homozygous for mutation c.700G>A (p.D234N) in the CBS gene. Both mutations have been previously reported but involve hypermutable CpG dinculeotides and may be recurrent mutations in the Qatari population. The results of this study illustrate a strong founder effect causing a high prevalence of an autosomal recessive disease in a highly consanguineous Arabian population. Molecular neonatal screening may be suitable for early detection of homocystinuria in this population.