Variation in the level of fetal hemoglobin in (δβ)°‐thalassemia heterozygotes with different numbers of α‐globin genes

The Sicilian type of (αβ)°‐thalassemia characterized by a ˜13 kb deletion, was present in a Turkish boy who is a homozygote and in his heterozygous parents who are first cousins. The father with ˜21% Hb F had five α‐globin genes (αα/ααα) and the mother with ˜10% Hb F had an α‐thal‐2 heterozygosity (αα/‐α). The difference in Hb F level is explained by a decreased formation of α₂γ₂ tetramers in the mother with an α‐chain deficiency while the extra α‐globin gene in the father will promote Hb F production.