[Genetically based states of elevated quantity of foetal haemoglobin (Hb F) in healthy individuals and patients].

During human development, the switch from foetal gamma- to adult beta-globin on chromosome 11p is not complete resulting in the residual gamma-globin expression in a modest subpopulation of erythrocytes termed "F-cells". Genetic determinants that are responsible for higher level of Hb F include various mutations within the beta-globin gene cluster as well as singular nucleotide polymorphisms in other loci associated with Hb F quantitative trait, and also epigenetic mechanisms. All these molecular conditions may drive to hereditary persistence of foetal haemoglobin (HPFH). Taking into account a morphologic criterion, HPFH is called pancellular (p-) HPFH, if the increased Hb F is distributed in a uniform fashion among all of the red cells. When the Hb F distribution is restricted, the syndrome is referred to as heterocellular (h-) HPFH. The Hb F persistence rarely occurs in healthy adults or accompanies certain hemoglobinopathies changing substantially phenotypic diversity of sickle cell disease and beta-thalassaemia.