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

Among several hundred apparently healthy Yugoslavian adults with slightly elevated levels of fetal haemoglobin, we have identified two distinct abnormalities, (a) A ^Gγ^Aγ(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; Carèet 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 C→T 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.