Hb Chad or alpha 223(B4)Glu----Lys beta 2 observed in members of a Surinam family in association with alpha-thalassemia-2 and with Hb S.

Three different hemoglobinopathies, i.e. Hb S, Hb Chad [alpha 23 (B4)Glu----Lys], and alpha-thalassemia-2 (-3.7) have been observed in eight members of a family from Surinam. The proposita had all three abnormalities, while her mother and four of her half-brothers had Hb Chad together with an alpha-thalassemia-2 heterozygosity or homozygosity. Gene mapping and dot-blot analysis of amplified DNA identified a G----A mutation in codon 23 of the alpha 2 alpha 1 hybrid gene resulting in the Glu----Lys substitution. The quantity of the alpha-Chad chain averaged 31.5% in its carriers with an additional alpha-thalassemia-2 heterozygosity [-alpha Chad(-3.7 kb)/alpha alpha], and 43% in the two carriers with an additional alpha-thalassemia-2 homozygosity [-alpha Chad (-3.7 kb)/-alpha (3.7 kb)]. These quantities are considerably higher than those reported for families from Chad, China, and Japan; the low levels of 14.5-24% Hb Chad in members of previously reported cases suggest a mutation on a chromosome with two alpha-globin genes [alpha alpha Chad/alpha alpha or alpha Chad alpha/alpha alpha].