Prevalence of common α-thalassemia determinants in south Brazil: Importance for the diagnosis of microcytic anemia.

Alpha thalassemia has not been systematically investigated in Brazil. In this study, 493 unrelated individuals from the southernmost Brazilian state of Rio Grande do Sul were screened for deletional forms of α-thalassemia. One hundred and one individuals had microcytic anemia (MCV < 80 fL) and a normal hemoglobin pattern (Hb A (2) < 3.5% and Hb F < 1%). The subjects were screened for - α(3.7) , - α(4.2) , - α(20.5) , - (SEA) and - (MED) deletions but only the - α(3.7) allele was detected. The - α(3.7) allele frequency in Brazilians of European and African ancestry was 0.02 and 0.12, respectively, whereas in individuals with microcytosis the frequency was 0.20. The prevalence of α-thalassemia was significantly higher in individuals with microcytosis than in healthy individuals (p = 0.001), regardless of their ethnic origin. There were also significant differences in the hematological parameters of individuals with - α(3.7) / αα, - α(3.7) /- α(3.7) and β-thalassemia trait compared to healthy subjects. These data suggest that α-thalassemia is an important cause of microcytosis and mild anemia in Brazilians.