Sickle cell anemia in the state of Maranhão: a haplotype study

Sickle cell anemia (SCA) is the most severe form of sickle cell disease caused by homozygosity of the β^S-gene (S/S or β^Sβ^S) and has worldwide distribution. Six polymorphic sites in the β-globin gene cluster were analyzed from a sample of 56 chromosomes of patients with SCA from the state of Maranhão, northeastern Brazil. PCR-RFLP showed that the CAR haplotype was predominant with a frequency of 64.28%, followed by the BEN haplotype (28.57%). Atypical haplotypes were identified at a frequency of 7.15%. Genotypes CAR/CAR, BEN/BEN, and CAR/BEN were present in 46.43%, 10.71%, and 35.71% of patients, respectively. β-Globin haplotype determination is important not only for the monitoring and prognosis of patients with SCA, but it also serves to inform anthropological studies that contribute to elucidating any peculiarities associated with African influences that contributed to the ethnological, economic, cultural, and social formation of Brazil. The high frequency of the CAR/CAR and CAR/BEN haplotypes in this study, which are associated with low levels of fetal hemoglobin, may ultimately reflect a severe clinical course and poor prognosis in patients with SCA in Maranhão.