β-Globin Gene Cluster Haplotypes in a Cohort of 221 Children with Sickle Cell Anemia or Sβ⁰-Thalassemia and Their Association with Clinical and Hematological Features

BACKGROUND/AIMS: β(S)-Haplotype prevalence and its associations with clinical and hematological characteristics were assessed in Brazilian children with sickle cell anemia or Sβ⁰-thalassemia. METHODS: A retrospective randomized cohort study was undertaken with 208 SS and 13 Sβ⁰-thalassemia children derived from the Newborn Screening Program of the state of Minas Gerais. β(S)-Haplotypes were determined by PCR-RFLP. RESULTS: Thirty-nine percent of the SS subjects had the CAR/CAR genotype, 33% had CAR/Ben, 24% had Ben/Ben, 1% had CAR/Atp, 1% had Ben/Atp, and 1% had Arab-Indian/Ben; 1% could not be characterized. Of the Sβ⁰-thalassemia children, 5 were CAR/undefined, 2 were Ben/undefined, and 1 was CAM/undefined. There was no significant association between β(S)-haplotypes and the total Hb, Hb F, MCV, MCH, WBC, and reticulocyte count among the SS children. Likewise, no significant association was detected between β(S)-haplotypes and the frequency of acute chest syndrome episodes, blood transfusions, splenic sequestration, or cerebrovascular disease (high-risk/conditional transcranial Doppler ultrasonography or clinical stroke). A limited number of Sβ⁰-thalassemia children precluded valid analyses. CONCLUSIONS: The prevalence of β(S)-haplotypes in this study is in agreement with the historical records of African slaves brought to the state of Minas Gerais. Furthermore, β(S)-haplotypes CAR and Ben were not associated with any analyzed feature of children with sickle cell anemia.