Haemoglobin Variants, β-Thalassaemia and G-6-PD Types in Liberia

Abstract

Haemoglobin variants, β-thalassaemia and glucose-6-phosphate dehydrogenase (G-6-PD) types were studied in 702 individuals from Buchanan, Liberia. In this population haemoglobins S and C, β-thalassaemia and G-6-PD deficiency were found together. There was a considerable tribal variation. In the tribes of eastern Liberia the S- and C-genes were uncommon and the β-thalassaemia gene was rather frequent, while in western Liberia the S- and C-genes were more frequent and β-thalassaemia uncommon. In the central and northern parts the S- and β-thalassaemia genes were found together in relatively high frequencies, The rate of malaria infection was found to be lower in individuals with the sickle cell and β-thalassaemia traits than in individuals with haemoglobin AA, but the difference was not statistically significant. The frequency of the δ-chain gene B₂ was 1.4% in the total material and there was no significant tribal variation for this gene. The frequency of G-6-PD deficiency estimated in males was 16%.

Newborn Screening for Sickle Cell Disease in Liberia: A Pilot Study

“…Malaria is holoendemic in Liberia, therefore one might expect a uniform distribution of hemoglobin S alleles around the country. Thus, the historic finding of a geographical distribution of beta‐thalassemia alleles and S alleles, and the apparent persistence of this distribution by maternal ancestral county in our study population, is intriguing . In the Mediterranean, similar findings have been described and attributed to epistatic interactions, which prevent the coexistence of hemoglobin S, beta‐thalassemia, and alpha thalassemias at high frequencies .…”

“…Silent beta‐0‐thalassemia or HPFH alleles in Monrovia could explain this difference: if one additional silent allele was present in our population with an allelic frequency of between 2.4 and 8.2%, HWE could be restored. This is supported by historical data describing beta‐thalassemia alleles in Liberia with a prevalence of 1–8% in various regions . The nonsickling NBS hemoglobin phenotype of “F” represents diagnoses of either beta‐thalassemia major, homozygous HPFH, or heterozygous beta‐0‐thalassemia with HPFH, confirming that these silent alleles exist within the study population .…”

“…Similar interactions may be at play in Liberia, although our sampling method has some important limitations (Fig. C) . In our study, S alleles in subjects with SCT were assigned to mothers in the study, as fathers were not reliably available.…”

“…Pioneering investigations of hemoglobinopathies in West Africa conducted prior to 1980 revealed a hemoglobin S carrier prevalence in Liberia ranging from 7 to 28%, varying among studies of adults, children, or both, and by region . These investigations highlighted Liberia as a unique country in West Africa with beta‐thalassemia trait present in up to 9% in some regions, localized to ethnic groups and regions where the allelic frequency of hemoglobin S was low . Specifically, hemoglobin S and hemoglobin C were more common in the west of the nation, whereas beta‐thalassemia trait was more common in the east .…”

Serum Protein Polymorphisms in a Liberian Population

“…In a study of Nigerian blood donors, Olusi et al [1981] found a rather high frequency of the S gene (around 10%), which they thought related to the high frequency of sickle-cell trait carriers in the Nigerian population. How ever, although around 8% of the Bu chanan population are heterozygous for hemoglobin S [Willcox and Beckman, 1981], we observed no individuals with the cq-antitrypsin S gene in a sample of 224 persons from this population.…”