GγAγ(δβ)°‐thalassaemia and a new form of γ globin gene triplication identified in the Yugoslavian population

Summary Among several hundred apparently healthy Yugoslavian adults with slightly elevated levels of fetal haemoglobin, we have identified two distinct abnormalities, (a) A GγAγ(δβ)°-thalassaemia heterozygosity with an ∼ 15 kb deletion which involves part of the δ globin gene and the β globin gene. This deletion is probably the same as that seen among Italians (Ottolenghi et al, 1982; Careet al, 1984). (b) A nondeletion form of hereditary persistence of Hb F which is caused by a γ globin gene triplication of the (+)Gγ mD (+)Gγ mD Aγ type. It is characterized by the presence of some 5% Hb F in the heterozygote containing nearly 100%Gγ chains. The CT mutation at position — 158 5’to the Gγ chain [(+)Gγ], identified through analyses of Xmn I digests, was present at both Gγ globin genes. This mutation is known to be associated with increased Gγ chain production (Gilman & Huisman, 1985), and thus is responsible for the increased Gγ chain production in these heterozygotes. The condition is different from the (+)Gγ mD (+)Gγ nondeletion type of HPFH which has been observed in heterozygotes of two Black families, and is associated with the presence of 3–4% Hb F (with mainly Gγ chains) in heterozygotes.