Molecular Basis of A-Thalassa in Portugal

Abstract

We have estimated the incidence and molecular basis of α-thal-assemia in a Portuguese population, mostly from the Greater Lisbon area. In a group of 100 consecutive cord blood samples, the gene frequency of the rightward deletion (-α^3.7) was 0.035, and the leftward deletion (-α^4.2) was 0.015. In this group, we have also found four heterozygotes for the triple α-globin gene rearrangement (ααα^anti3.7 gene frequency 0.020). We have characterized the subtypes of -α^3.7 and ααα^anti3.7 rearrangements. On the whole, these results give an incidence of 10% for deletional a-thalassemia carriers in the studied Portuguese population In a group of 342 subjects presenting β-thalassemia, or Hb S trait, β-thalassemia major, sickle cell disease or low red blood cell indices, the -α^3.7, -α^4.2, –^SEA –^MED (αα)^MM and ααα^anti3.7 haplotypes were found in different combinations. Only one nondeletional α-thalassemia determinant (a 5 nucleotide deletion in the α2-globin gene in the second intervening sequence donor site) was detected, which might suggest a low incidence of these defects in the Portuguese population