Hemoglobin Windsor or beta 11 (A8)Val----Asp: a new unstable beta-chain hemoglobin variant producing a hemolytic...

A new beta-chain variant, Hemoglobin Windsor [beta 11 (A8)Val----Asp] was discovered in a 9-month-old child who presented with a hemolytic anemia of 59 g/l with an intercurrent viral infection. Her blood film demonstrated fragmented cells, target cells, stipple cells, nucleated red cells, polychromasia and some spherocytes, indicative of acute hemolysis. Hemoglobin electrophoretic studies were requested and a beta-chain variant, constituting 27% of the total hemoglobin, separated towards the anode under alkaline conditions. The variant was unstable, producing numerous "Hb H"-like inclusions and a positive isopropanol stability test. The variant hemoglobin was purified by precipitation. The variant beta-chain was purified by column chromatography and its tryptic peptides fractionated by high performance liquid chromatography. Amino acid analysis and sequence data indicated that the valine at position 11(A8) had been substituted by an aspartic acid residue. This substitution, in the bottom of the heme pocket, has resulted in instability of the hemoglobin molecule and an increase in oxygen affinity. The variant appears to have resulted from a spontaneous mutation as both parents are hematologically normal. A younger sibling is also hematologically normal.