HB A2-Canada Or A α2δ2 99(G1) ASP → ASN, a Newly Discovered Delta Chain Variant With Increased Oxygen Affinity Occurring In Cis to β-Thalassemia

An Indian family is described in which the father has a δ chain abnormal hemoglobin which is the result of a mutation of the δ gene in cis to a β-thalassemia heterozygosity. The abnormality concerns a substitution of the Asp residue in position 99 (G1) by an Ash residue. A similar substitution has been found in the β chain of Hb Kempsey (α2β2 99 Asp → Asn). The observed abnormality results in a greatly increased oxygen affinity of this newly discovered Hb A2 variant.