Interaction between Homozygous β0 Thalassaemia and the Swiss Type of Hereditary Persistence of Fetal Haemoglobin

Abstract

The interaction between β⁰ thalassaemia and an heterocellular form of hereditary persistence of fetal haemoglobin (HPFH), presumably of the Swiss type, has been studied in three generations of a family in which both traits occur. The haematological parameters and the segregation of the two characters in the family suggest that the propositus, a 52-year-old male from southern Sardinia, is homozygous for β⁰ thalassaemia and carrier of the HPFH. In spite of the complete suppression of adult haemoglobin synthesis, the patient is not anaemic and shows only morphological abnormalities of the red cells associated with a moderate decrease of the erythrocyte life span. Studies of the synthesis of haemoglobin chains in vitro have revealed only a mild degree of unbalance in the propositus, with a γ/α ratio of 0–67, and a very slight unbalance in a 3-year-old child heterozygous for β thalassaemia and HPFH. Preliminary analysis of the linkage between this kind of heterocellular HPFH and the β Hb locus has been performed, utilizing all the suitable families reported in the literature. Although positive lod scores (1.535) have been obtained at a recombination fraction of 0.20, the data available are not sufficient to conclude in favour or against the linkage between the β Hb locus and the heterocellular type of HPFH.