Haplotypes of βSChromosomes Among Patients with Sickle Cell Anemia from Georgia

Abstract

Fetal hemoglobin and G.gamma. levels have been correlated with the presence or absence of eight restriction sites within the .beta. globin gene cluster (haplotypes) for numerous sickle cell anemia patients from Georgia. The most common haplotypes were #19 (Benin) and #20 (CAR); all patients with haplotype combinations 19/19, 20/20, and 19/20 were severely affected with low Hb F and low G.gamma. levels. A modified #19 .beta.S chromosome with a -G.gamma.-G.gamma.- globin gene arrangement, instead of -G.gamma.-A.gamma.-, was present in SS and SC newborn babies with G.gamma. values above 80%. Haplotype #3 (Senegal) was present among 15% of the .beta.S chromosomes; the two adult patients with the 3/3 combination were mildly affected with high Hb F and G.gamma. values. The haplotype AT with the variant A.gamma.T chain was a rarity. A new haplotype was found in one 17-year-old SS patient and five of his Hb S heterozygous relatives. This haplotype is associated with an increased production of Hb F in heterozygous and homozygous Hb S individuals; this Hb F contained primarily A.gamma. chains. A comparison was made between the different haplotypes among SS patients and normal Black individuals, and a remarkable similarity was noted in the fetal hemoglobin data for subjects with these different chromosomes.