A novel rearrangement of the human fetal globin genes leading to a six gamma-globin gene haplotype.

Haematological as well as gene mapping data are reported for three members of a Portuguese Caucasian family with high G(gamma)-globin levels. A gamma-globin gene sextuplication of the G(gamma)AG(gamma)AG(gamma)AG(gamma)AG(gamma)A(gamma) type was present in the proband and her father. Comparison of gene mapping data with quantitative results of fetal haemoglobin (HbF) analysis provided an explanation for the extremely high G(gamma)-globin levels (> 90%) in the HbF from the two mentioned individuals. This rearrangement, for which a generation mechanism is proposed, is the first gamma-globin gene sextuplication described in the literature.