The genetic architecture of the β-globin chain in individuals with and without sickle cell disease in Nigeria: A case for beta thalassemia?

BackgroundReports on beta thalassemia in the Nigerian population are conflicting, and the prevalence and role of beta thalassemia in Nigerian sickle cell disease (SCD) patients remain unclear. There is a need to set the records straight to ascertain the prevalence and effect of beta thalassemia in these patients. Methods123 SCD patients and 117 age- and sex-matched controls were recruited. For the cases, the age range was 3 - 69 years, median(IQR) = 16(9 - 29). A separate cohort of 26 SCD patients were studied along. Full blood count was calculated, and the hemoglobin fractions were estimated by High Performance Liquid Chromatography. The 1.6kb beta-globin gene region was amplified from germline DNA and Sanger sequencing was performed. Single nucleotide polymorphisms (SNPs) were detected and annotated, and haplotypes were constructed. ResultsContrary to recent reports, the prevalence of beta thalassemia in this population is <1%. Aside the sickle, hemoglobin C and beta thalassemia mutations, eight other variants were identified. Only three of these variants were found in the SCD patients and are in linkage disequilibrium. The sickle and hemoglobin C mutations arose on the major ancestral haplotype, while the beta thalassemia intermedia mutation (rs33915217C>A) was found on the minor ancestral haplotype, atypical of Africa. Two rare variants (rs537944366T>C and rs33915217C>A) are reported for the first time in the Yoruba population. ConclusionThere is a need for a re-assessment of the diagnosis of beta thalassemia in this and other African populations for the proper management of SCD and other anemia-related cases.