The Hb F composition in a Moroccan family with beta zero-thalassaemia and Hb O-Arab.

We report on a Moroccan family in which the proposita displays a picture of beta-thalassaemia intermedia, associated with heterozygous Hb O-Arab (beta 121 Glu----Lys) and a beta zero-thalassaemia trait. Hb O-Arab was ascertained by the disappearance of the Eco RI restriction site that normally overlaps the beta-globin gene codon 121. The proposita further presents high proportions of Hb F (12.1%) and of G gamma chains (68.6%). The transmission of the proband's haemoglobin markers was analyzed (the proband's husband displaying normal haemoglobin). The beta zero-thalassaemia and O-Arab genes underwent mutual exclusion. A high Hb F (9.28%) level was found in one child, in association with the beta zero-thalassaemia trait, while another child carrying the latter trait displayed normal levels of Hb F. This situation suggests that a heterocellular HPFH determinant is involved. However, there was no means to establish whether the high Hb F proportion in the mother results solely from the beta zero-thalassaemia -Hb O-Arab association or whether an additional HPFH determinant is present. No DNA deletion was detectably associated with the high proportion of Hb F. In this family, the G gamma percentage was high whenever the beta zero-thalassaemia gene was present, regardless of total Hb F percentage. This observation is consistent with the view that the control of the G gamma percentage in the adult is linked to the beta-locus.