Elevated Hb F associated with beta-thalassaemia trait: haemoglobin synthesis in reticulocytes and in blood BFU-E.

The red cells of a patient heterozygous for beta-thalassaemia contained 19% fetal Hb. Study of his family suggested that the proband had inherited the Swiss type of hereditary persistence of fetal Hb (HPFH) from his mother who is not thalassaemic and possessed 1.37% of Hb and 11% F-cells. Studies of globin synthesis showed a similar imbalance in the heterocellular HPFH-beta-thalassaemia compound heterozygotes and in the heterozygous beta-thalassaemic members of the family. Age stratification of the red cells showed a slight enrichment in Hb F and a decreased Hb A2 level in the older cell populations. Hb F production in the BFU-E colonies of the proband was higher than that found in vivo and in other beta-thalassaemic heterozygotes in culture. Study of single erythroid burst colonies showed a marked heterogeneity in Hb F synthesis from one colony to another, while the pool of free alpha-chains remained of similar magnitude. It is suggested that in the proband, the HPFH gene, which is in trans with respect to the beta-thal-gene, increases the size of the F-cell population and its activity is carried on at the expense of the normal beta A gene.