Hemoglobin abnormalities in a black family with HB S, hereditary persistence of HB F, and a gamma chain variant; a reevaluation through gene mapping

Abstract

Members of a Black family from Georgia who were investigated for the first time in 1960 and several times thereafter were reinvestigated through DNA restriction endonuclease analyses and haplotyping, while the gamma chain heterogeneity of the Hb F was reevaluated using a newly developed HPLC procedure. Four different abnormalities were present. (a) Heterozygosity for G gamma A gamma-HPFH type II characterized by a large deletion involving the delta and beta globin genes with a 5' end within the psi beta gene. (b) Heterozygosity for an -epsilon-G gamma-G gamma-psi beta-delta-beta S-chromosome, thus carrying a beta S globin gene and two G gamma genes instead of one G gamma and one A gamma gene. (c) Heterozygosity for an -epsilon-G gamma-A gamma T-psi beta-delta-beta S-chromosome, carrying the beta S globin gene and an allele of the A gamma (or A gamma I) gene. These three chromosomes occurred in combination with each other, resulting in SS and S-HPFH conditions, and with a normal -epsilon-G gamma-A gamma-psi beta-delta-beta A-chromosome resulting in the HPFH and Hb S heterozygosities. The presence of the -G gamma-G gamma- and -G gamma-A gamma T-chromosomes in the one SS patient was responsible for the high G gamma value (average 75%), 25% A gamma T chain, and for the absence of the A gamma I chain. (d) An alpha-thalassemia-2 heterozygosity in one member.