alpha-Thalassaemia in Tunisia: some epidemiological and molecular data.

Unlike the other haemoglobinopathies, few researches have been published concerning alpha-thalassaemia in Tunisia. The aim of the present work is to acquire further data concerning alpha-thalassaemia prevalence and molecular defects spectrum in Tunisia, by collecting and studying several kinds of samples carrying alpha-thalassaemia. The first survey conducted on 529 cord blood samples using cellulose acetate electrophoresis, have displayed the prevalence of 7.38% Hb Bart's carriers at birth. Molecular analyses were conducted by PCR and DNA sequencing on 20 families' cases from the above survey carrying the Hb Bart's at birth and on 10 Hb H diseased patients. The results showed six alpha-globin gene molecular defects and were responsible for alpha-thalassaemia: -alpha(3.7), - -(MedI), alpha(TSaudi), alpha(2)(cd23GAG->Stop), Hb Greone Hart: alpha(1)(119CCT->TCT) corresponding to 11 genotypes out of which two are responsible for Hb H disease (- -(Med)/-alpha(3.7)) and (alpha(TSaudi)alpha/alpha(TSaudi)alpha) and a newly described polymorphism: alpha+6C->G. The geographical repartition of alpha-thal carriers showed that the -alpha3.7 deletion is distributed all over the country, respectively the alpha(HphI) and alpha(TSaudi) seem to be more frequent in the central region of the northeast region. The haematological and clinical data showed a moderate phenotype with a late age of diagnosis for Hb H disease. This work had permitted, in addition to an overview on alpha-thalassaemia in the country, the optimization of protocols for alpha-thalassaemia detection in our lab, allowing further investigations concerning phenotype-genotype correlation in sickle cell disease or beta-thalassaemia.