24th May 2023

Foetal haemoglobin (HbF) and sickle cell

HbF is composed of two alpha chains and two gamma chains. Unlike HbS, HbF does not enter the polymerization phase when sickling occurs and helps to slow this process. This explains why patients are asymptomatic in the first few months of life, when HbF is the predominant haemoglobin type. Hydroxycarbamide is a treatment used in sickle cell disease which increases the production of gamma globin chains, resulting in increased levels of HbF.

Some individuals have hereditary persistence of foetal haemoglobin, where high levels of HbF are due to beta-globin gene deletions or point mutations in the promoters of the HbF genes.