Molecular Analysis of β-Thalassemia Cases in Poland.

β-thalassemia is a heterogenous, inherited disease resulting from reduced or absent synthesis of β-globin chain of haemoglobin. This disorder is very common in the Mediterranean, Middle Eastern, African and South-East Asian populations. The aim of the present investigation was to verify a common view that thalassemia in Poland is a very rare disease. 600 patients (270 men and 330 women), aged 2–85 years, with microcytosis and no evidence of iron deficiency, were examined for β-thalassemia. Hemoglobin A₂ was increased in 106 patients. In 48 patients there was also an elevation of hemoglobulin F and in 42 patients of serum bilirubin.

All 106 patients were examined for 8 common Mediterranean mutations. 7 different mutations were detected in 46 heterozygous patients (number of patients wit a particular mutations are in square brackets): IVS1-6(T>C) [15]; IVS2-745(C>G)[14]; IVS2-1(G>A) [10]; IVS1-1(G>A) [2]; CD6-A [2]; CD39(C>T) [2]; IVS1-110(G>A) [1].

We also discuss the effect of these mutations on the expression level of the β-globin gene. Frequencies of individual mutations in Poland were different from those encountered in Mediterranean and some Centrak European countries. We also detect two novel mutations:

IVS-1-1(G>A) G^GTTGGT>AGATTGGT and 5′UTR; +33(C>T). The first novel mutation significantly decreased the mRNA level of the β-globin gene. The second mutation seems to be silent and does not affect β-globin synthesis. In this case, this particular mutation occurs with IVS-1-6(G>C) mutation in compound the heterozygotes stage.