Hemoglobinopathies in North Africa: a review

Abstract

Hemolytic anemias are very common diseases. Among these diseases, hemoglobinopathies are widely spread throughout the Mediterranean Basin, including North Africa (Tunisia, Algeria and Morocco). Their severity and disabling nature make them a major public health problem. This study includes our data on the Tunisian hemoglobinopathies together with all the reports concerning epidemiological, clinical and molecular aspects in Algerian and Moroccan populations. Investigation methods begin with the application of several techniques for hemoglobin (Hb) analyses [electrophoresis and isoelectric focusing (IEF), micro-chromatography assay] of anemic patients in various hospital departments. Molecular investigation by DNA analyses completes the hematological and biochemical studies using polymerase chain reaction (PCR) followed by enzymatic digestion and/or denaturing gradient gel electrophoresis (DGGE), single strand conformation polymorphism (SSCP) and sequencing. These methods offer screening for a large number of families affected by sickle cell disease and thalassemia. In Tunisia, Algeria, and Morocco, more than 45 mutations have been identified on the beta-globin gene. The most common in Tunisia and in Algeria are codon 39 (C>T) and IVS-I-110 (G>A), which together account for more than 50% of all mutations. In Morocco, the predominant mutations are codon 39 and frameshift codon (FSC) 8 (-AA). The identification of molecular defects in the betagene contributes to the development of diagnostic tests (prenatal diagnosis), and gives us the opportunity to help many couples. Our studies of the haplotypes of the beta(S), codon 39 and IVS-I-110 origins allowed the hypothesis of a Benin origin for beta(S), a local North African origin for codon 39 and an Eastern Mediterranean origin for IVS-I-110. The analysis of polymorphisms associated with a moderate phenotype of beta-thalassemia (beta-thal) and sickle cell disease in North Africa has shown, in several cases, a strong association with some mutations and restriction fragment length polymorphisms (RFLP) haplotype IX on the beta-globin locus and the -158 (C>T) polymorphism in 5' on the (G)gamma-globin gene. Finally, more knowledge on the regulation of the beta-globin locus may contribute to the improvement of investigation, monitoring and treatment of hemoglobinopathies.