[Screening of hemoglobinopathies and molecular analysis of beta-thalassemia in Central Tunisia]

Previous investigations have permitted to locate 16 beta-thalassemic mutations in different samples of the Tunisian population. One of them (IVS I nt 2: T--G) had been found only in the central region of Tunisia. Our research was carried out in this part of the country to estimate the prevalence of this mutation and to establish a prenatal diagnosis using appropriate probes.

One thousand one hundred and five blood samples taken from 1987 to 1990 from healthy blood donors and 346 samples taken from 1985 to 1992 from patients were analysed. Detection of hemoglobinopathies was carried out by means of specific hematological tests and different electrophoretic and chromatographic techniques. Mutations were detected by means of the usual techniques of molecular biology.

Sickle cell anemia and beta-thalassemia were the most frequent in the samples studied. The molecular analysis carried out on eight patients native of the Essouassi-El-Djem region point out that all these patients carry the same point mutation (IVS I nt 2: T-G) detected for the first time in 1988 in a patient native of the same region. One of these patients, aged 43, who did not suffer from anemia and did not show the usual symptoms of beta O thalassemia, had one hemolytic attack at the age of 17.

The high number of persons carrying Hb S and beta-thalassemia trait increase the risk of appearance of homozygous forms. The presence of the same mutation IVS I nt 2: (T-G) in all beta O-thalassemic patients from Essouassi-El Djem region may indicate that it may have its origin there. The heterogeneity of clinical phenotype of these patients shows the difficulty of establishing a unique strategy of prenatal diagnosis by DNA analysing which can be applied in all cases.