Clinical, hematological and genetic features of sickle-cell anemia and sickle cell-beta thalassemia in a Brazilian population.

Clinical, hematological and genetic studies were carried out on 40 patients with symptomatic sickle-cell disease, selected on the basis of a predominant HbS fraction and absence of other abnormal hemoglobin variants. Family studies showed they included 26 homozygotes for the sickle-cell gene (SS) and 14 double heterozygotes for both the sickle-cell and the (0)beta-thalassemia genes ((S)(0)beta-thalassemia). Comparison of the two groups revealed the more common occurrence of splenomegaly, lower MCV and mCH, and higher HbA2 in (S)(0)beta-thalassemia. Total hemoglobin was slightly lower in SS disease but the difference was not significant. Fetal hemoglobin (HbF) was moderately elevated to similar levels in both groups. These results suggest a high incidence of S beta (0)-thalassemia in certain Brazilian mixed populations and confirm the severity of the double heterozygous state. The distinction between the two disorders is often difficult, but can be made on the basis of the hematological data taken together with family studies.