Hemoglobin Westmead α₂ 122(H5)His←Gln_β2: A New Hemoglobin Variant with the Substitution in the α₁β₁ Contact Area

Abstract

A new hemoglobin variant, hemoglobin Westmead α₂ 122(H5)His←Gln_β2, was detected in a 30-year-old Chinese female whose condition, at first presentation, was diagnosed as iron deficiency anemia. The anemia responded to iron therapy, however, abnormal red cell changes were still evident. The possibility of a hemoglobinopathy was then investigated.

Hemoglobin Westmead could not be separated from hemoglobin A by electrophoresis at alkaline or acid pH. Red cell inclusions, noted after 16 hrs incubation at 37°C with new methylene blue stain, provided the first laboratory evidence of the possible presence of a hemoglobin variant. By globin chain electrophoresis at pH 6.4 and column chromatography, the variant α-chain of hemoglobin Westmead was separated from the normal α-chain, the approximate proportion of the variant α-chain to the total α-chain being 50%.

The proportion of the variant and the demonstration of occasional HbH cells, after 2 hrs incubation in new methylene blue stain and brilliant cresyl blue stain, suggested the possibility that the proposita also has α-thalassemia trait.

The substitution in hemoglobin Westmead is in the fifth residue of helix H of the α-chain. The histidine residue at that location in the normal hemoglobin molecule is involved in the α₁β₁ contact area.