[Hemoglobinopathies in Tunisia. An updated review of the epidemiologic and molecular data].

The hemoglobinopathies affect the blood red cells and are the most common monogenic diseases worldwide. The high frequency and clinical severity of the hemoglobinopathies, make them a major public health problem. We report here an updated review on epidemiologic and molecular data of the hemoglobinopathies in Tunisia. From 1980 to 2005, a screening of hemoglobinopathies was performed on a total of 44299 individuals according to 2 kinds of work: a systematic screening on several populations (24240) from different regions of the country and a cohort of individuals referred to our laboratory for hemoglobinopathies suspicion (20059). Blood was collected in EDTA tubes from the studied individuals to determine the hematological parameters, the hemoglobin electrophoretic data and the iron status. DNA analysis was performed by the usual PCR based-procedures for the molecular defects identification. Systematic surveys allowed us to show an average prevalence of hemoglobinopathy carriers of 4.48% reaching 12.50% in some focus regions. The average frequency of B-thal trait is of 2.21% and that of sickle cell trait is of 1.89%. Hemoglobin screening on newborns has shown a frequency of alpha-thal trait of 5.48%. Oriented studies from our hospital experience allowed us to list more than 2394 major forms. Molecular analysis on beta-thalassemia patients allowed to identify 21 different alleles. The two most frequent mutations (cd39 C-->T and IVS1-110 G-->A) accounted for 70% of the total encountered beta-thal mutations. Among the other mutations, three were described for the first time in the world on Tunisian families. The sickle cell disease is associated with the Benin haplotype in 95% of the studied cases. Concerning alpha-thal mutation, the - alpha37 deletion was the most common. We also note the identification of several rare Hemoglobin variants as well as diverse associated forms of anomalies. Knowledge of epidemiological and molecular data of hemoglobinopathies is fundamental to understand the mechanisms of disease expression and the genotype / phenotype correlations. Furthermore, the distribution of the hemoglobinopathies in the regions allows to orientate efficiently the planning tasks regarding control and prevention of these hereditary diseases.