Approximately 1% of persons with homozygous sickle cell disease also demonstrates hereditary persistence of fetal hemoglobin (HPFH). Persons with HbS/HPFH have a milder anemia than individuals with SCD who have none to normal levels of HbF.
Increased fetal hemoglobin protects the cell from sickling because of its higher affinity for oxygen. HPFH may also be present in other hemoglobinopaties and thalassemias or in SCD in combination with other hemoglobins (HbSC/HPFH) and thalassemia (HbS/Bthal/HPFH).
