Haplotypes and α globin gene analyses in sickle cell anaemia patients from Kenya

Abstract

Over 60 patients from the Luo and Luhya tribes of Western Kenya, aged 1–23 years. with severe sickle cell anaemia were evaluated through haematological and gene mapping analyses. Nearly all (56 of 58 tested) were homozygous for haplotype 20 (Antonarakis et al, 1984) which is also frequently present in SS patients of the Central African Republic. All patients had a severe haemolytic anaemia with low Hb F levels and low levels of Gγ chains. An α‐thalassae‐mia‐2 heterozygosity (‐α/αα; ‐ 3·7 kb deletion) was present in 26 of 53 patients tested: one patient was a homozygote [f(—α) = 0·255]. The α‐thal‐2 was type I in all but one subject with this deficiency; the one exception had an α‐thal‐2 heterozygosity, type II. Heterozygosity for the α‐thal‐2 did not affect the clinical condition nor the haematology; Hb F levels were somewhat lower in SS patients with —α/αα than in those with αα/αα. A high frequency was observed for the absence of an Xba I restriction site 5′ to the ξ globin gene; the frequency of this anomaly [f(Xba I‐)] was estimated at 0·39 for the chromosome with two α globin genes and at 0·74 for that with the α‐thal‐2 deletion. An Apa I restriction site polymorphism was observed in the IVS‐II of the α2 globin gene; 13 α2 genes of 53 normal (αα/) chromosomes had this restriction site which was absent in the hybrid α globin gene of the —α/ chromosome.