A new type of hereditary persistence of fetal haemoglobin (HPFH): HPFH Tunisia beta + (+C-200)G gamma.

Nd-HPFH are haematological conditions which are natural models to aid understanding of the haemoglobin (Hb) switch. In this paper we describe a new non-deletional hereditary persistence of fetal haemoglobin (nd-HPFH) associated with the highest Hb F level observed to date (up to 49% without haemopoietic stress). Sequence of the G gamma promoter revealed a cytidine insertion within a stretch of four cytidines, located between -200 and -203 bp with respect to the cap site. This insertion is situated within a polypyrimidine-polypurine region which can adopt a triple helix structure, and is therefore of particular interest with respect to the Hb switch mechanism.