The frequency of βS-globin haplotypes in the state of Paraná, Brazil, and clinical manifestations of sickle cell anemia

Abstract

ABSTRACT Introduction: Haplotypes in the β S-globin cluster are named according to their geographical origin as Central African Republic (CAR), Benin (BEN), Senegal (SEN), Cameroon (CAM) and Arab-Indian. They are considered to have influence on the diversity of clinical manifestations in sickle cell anemia (HbSS). Objective: To identify β S haplotypes and genotypes, their frequencies and their probable association with clinical presentation in patients with sickle cell anemia in the state of Paraná. Method: Longitudinal and descriptive study for the definition of haplotypes, and associative study for analysis of their influence on clinical severity. By polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), polymorphic regions of 100 HbSS patients were identified. The association of haplotypes with clinical manifestations was analyzed in a subset of 52 pediatric patients. Results: In the state of Paraná, haplotype frequencies were: CAR: 76% BEN: 17.5% SEN: 0.5%, CAM: 0.5% and Atypical (Atp): 5.5%. Genotype frequencies were: CAR/CAR: 62%; CAR/BEN: 20%; CAR/Atp: 6%; CAR/ SEN: 1%; CAR/CAM: 1%; BEN/BEN: 6%; BEN/Atp: 3%, Atp/Atp: 1%. The average percentage of fetal hemoglobin (HbF) in CAR/CAR and CAR/BEN patients was higher than in other studies. Clinical manifestations were not influenced by β S haplotypes. Dactylitis and splenic sequestration occurred more frequently in children below 3 years of age. Conclusion: In this study, no association was found between haplotypes and clinical manifestations, probably given the almost absolute predominance of CAR and BEN haplotypes. However, this fact alerts to the possible influence of other polymorphisms and miscegenation in the Brazilian population.

Keywords

• sickle cell anemia
• pediatrics
• haplotypes