A neonatal screening survey of α-thalassemia (α-thal) among the United Arab Emirates (UAE) nationals was conducted on 418 consecutive cord blood samples. Our findings demonstrate that 49% of the cases studied were found with an α-globin gene defect. The gene frequency of the –α^3.7 was 0.2847 and that of the –α^4.2 was 0.0072. Four nondeletional α-thal mutations were found; α^PA-1, α^PA-2, Hb CS and α^-5nt del with gene frequencies of 0.0036, 0.0012, 0.0024, and 0.0072, respectively. We also report here the genotype-phenotype correlation in 22 patients with Hb H disease or Hb H-like syndrome. Of these, 6 were homozygous for the α^PA-1 mutation, 2 were homozygous for Hb CS, and 14 were compound heterozygous for either α^PA-1, Hb CS, α^-5nt del or ––MED-I, with the –α^3.7. The data reported here demonstrate that a considerable heterogeneity of α-thal mutations occurs in the UAE and that the incidence of α-thal in the indigenous population is one of the highest in the world. Our clinical data suggest that Hb H disease in the UAE has, in general, a mild to moderate phenotypic presentation.

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The Dubai Thalassemia Center has identified 35 different beta-thalassemia mutations in 570 chromosomes from the United Arab Emirates population using gene amplification, hybridization with specific labeled oligonucleotide probes, sequencing of amplified DNA, restriction enzymes, and amplification refractory mutation system techniques. This large number of mutations which represent 21% of the total beta-mutations discovered worldwide reflects the heterogenous nature of the population living in the United Arab Emirates (1). We found that 50% of our beta-thalassemia patients have a concomitant alpha-thalassemia; namely the -alpha 3.7 kb deletion. Co-inheritance of alpha-thalassemia especially in the form of two alpha-globin gene deletions have an ameliorating effect on the phenotype presentation of our beta-thalassemia. Nine patients (one homozygote and eight compound heterozygotes) were identified with Hb Monroe (IVS-I,-1 (G-->C)), a thalassemic hemoglobin characterized by an Arg-->Thr substitution in codon 30 of the beta-globin gene. In addition, one of the patients was a compound heterozygote for Hb Tacoma [IVS-I, +1 (G-->C)]; a point mutation affecting the third nucleotide of codon 30 (G-->C) causing an Arg-->Ser replacement.

This study is to identify the various beta-thalassemic alleles in the United Arab Emirates (UAE), and compare them with the UAE residents from neighboring countries suffering from the same problem. Gene amplification, dot-blot hybridization with synthetic probes, restriction enzyme analyses, and sequencing were the tools used. Thirteen different mutations were observed in the UAE patients and seventeen mutations in the non-locals. The IVS-I-5 (G-->C) Asian Indian mutation was the most frequent mutation in both groups. Homozygous mutations in both groups were relatively higher than double heterozygous mutations.

We have identified the beta s-globin gene haplotypes of 85 patients with sickle cell disease attending the Dubai Thalassemia Center and assessed the influence of haplotype, alpha-thalassemia, and fetal hemoglobin on the clinical presentation. Identification of the beta s haplotypes was based on mutation analyses in the promoter sequences of the G gamma- and A gamma-globin genes. The Arabian-Indian haplotype was found in 52% of the beta s chromosomes, whereas the remaining were the Bantu and Benin haplotypes. Those with the Arabian-Indian haplotype in this group had a significantly higher fetal hemoglobin (Hb F) level (mean 27%) and a milder clinical course. In contrast, those with the African haplotypes, Bantu and Benin, expressed relatively lower Hb F levels (mean 11.3%), with a severe clinical presentation. Coinheritance of alpha-thalassemia trait in the African haplotypes had an ameliorating effect on hemolytic episodes, but vaso-occlusive crises were more frequent.