Haemoglobin Inkster (α285 aspartic acid → valineβ2) Coexisting with β‐Thalassaemia in a Caucasian Family

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Abstract
Summary. Haemoglobin Inkster, a new α‐chain variant, was discovered in a family which also had the gene for β‐thalassaemia. The amino acid abnormality was in αTp‐9 which contains 29 amino‐acid residues. Structural studies were facilitated by cleavage of the abnormal α‐chains with cyanogen bromide followed by tryptic digestion. The substitution was shown to be valine for aspartic acid at position 85 in the α‐chain. Affected individuals had no haematological abnormalities. Individuals with both β‐thalassaemia and Hb Inkster had slightly lower percentages of Hb Inkster than those found in persons heterozygous for the Hb Inkster gene alone. ‘Interaction’ between thalassaemia and variant haemoglobin genes involving different haemoglobin loci has been reported in another family with β‐thalassaemia and an α‐chain haemoglobin mutant, as well as in the converse situation of coexisting β‐thalassemia and a β‐chain haemoglobin mutant. This decrease in the mutant haemoglobin percentage differs from the more common ‘interaction’ of thalassaemia and mutant haemoglobin genes involving the same haemoglobin locus, in which the mutant haemoglobin percentage is increased. The mechanism for the ‘interaction’ is unknown, but the presence of an unusually low percentage of a haemoglobin variant should warrant investigation for coexisting thalassaemia involving a different haemoglobin locus.