Postnatal changes in the quantities of globin chains and hemoglobin types in two babies with Hb H disease

Rapid and accurate quantitation of Hb Bart's and Hb H using weak cation exchange high performance liquid chromatography: correlation with the alpha-thalassemia genotype

The Bio-Rad Variant Hemoglobin testing system is an automated high performance liquid chromatography analyzer marketed with a beta-thalassemia short program to quantify Hbs F and A2, and assist in detecting Hbs A, S, D, C, and E. Although the two hemoglobins present in Hb H disease, Hb Bart's and Hb H, are separated by the system, they are not quantitated. In this study we modified the beta-thalassemia short program in order to facilitate quantitation of Hb Bart's and Hb H. Blood samples from 60 patients with Hb H disease, with various underlying genotypes, were studied. Analyses were performed on the day of blood collection or on hemolysates stored at -80 degrees C in cyanide or carbomonoxy forms. The mean sum of Hb Bart's and Hb H levels in all patients was found to be 12% (range 1.8-35%). Patients with nondeletional mutations (or association of alpha(0) deletion and nondeletional mutations) had notably higher Hb Bart's and Hb H levels when compared to patients with deletional genotypes.

Compound heterozygosity for two alpha-globin gene defects, Hb Taybe (alpha 1; 38 or 39 minus Thr) and a poly A mutation (alpha 2; AATAAA-->AATAAG), results in a severe hemolytic anemia

We have identified two alpha-globin gene variations in an Arabian male with severe hemolytic disease through sequencing of amplified DNA of his alpha 2- and alpha 1-globin genes. One of the abnormalities involves a CAC (ACC or CCA) deletion between codons 36 and 41 of the alpha 1-globin gene. This leads to the synthesis of an abnormal alpha chain with one instead of two threonine residues at positions 38-39 and to the formation of the unstable Hb Taybe. The second variation is a mutation located in the poly A site of the alpha 2-globin gene (AATAAA-->AATAAG) which is common among Arabian people. Family studies have shown that the two variations are located on opposite chromosomes. The hemolytic disease in this man, resembling Hb H disease, is likely the result of a severe downregulation of both alpha-globin genes on the chromosome with the alpha 2 poly A mutation, and the instability of the alpha-Taybe chain being the product of an alpha 1-globin gene; this leaves only one alpha 2-globin gene normally active.