Pesquisa das deleções -α3.7 e -α4.2 no agrupamento de genes da alfa globina humana e avaliação do perfil clínico-laboratorial em indivíduos com fenótipo de hemoglobina AS

Abstract

Abstract In Brazil, studies have shown a high frequency of the - α3.7deletion and rare reports of the -α4.2 deletion. This study aimedat evaluating individuals with the hemoglobin AS phenotype andinvestigating the presence of alpha thalassemia in this population.Sixty-one individuals with hemoglobin AS and AA phenotypeswere selected. All were submitted to molecular analysis of the -α3.7 and -α4.2 deletions and evaluation of hematologic, bio-chemical and urinary profiles. The mean VCM (79.85 fL ± 3.2)was significantly lower (p < 0.0001) in individuals with alphathalassemia. The mean serum iron concentration was significantlylower in individuals with the AA phenotype (77 mcg/dL ± 30 - p =0.013) compared to AS individuals (98 mcg/dL ± 34) however, bothlevels were within the normal range. The other parameters, in-cluding ferritin, transferrin, total iron binding capacity, total bi-lirubin, bilirubin fractions and lactate dehydrogenase showed nosignificant differences. Statistically significant differences werenot observed between the groups in respect to hemoglobinuriaand hematuria. The frequency of alpha thalassemia in the studiedpopulation was 25.0%. Of the AS individuals, 13.3% presentedinteractions with - α + thalassemia (- α3.7/αα). Among individualswith normal hemoglobin phenotypes, five (8.3%) were heterozy-gous for the -α3.7 deletion and one individual (1.7%) was het-erozygous for the -α4.2 deletion. One individual (1.7%) wasidentified with a non-identified alpha chain variant in associa-tion with - α + thalassemia (- α3.7/αα). The molecular diagnosisof alpha thalassemia (deletion of one gene) is of extreme impor-tance, both for patients with sickle cell trait and for individualswith the AA phenotype, even in the absence of altered hemato-logical parameters. It is important to remember that the use ofmicrocytosis and hypochromia as diagnostic criteria for alphathalassemia may underestimate the frequencies of this genetic al-teration.