Hereditary persistence of fetal hemoglobin (HPFH) is a benign condition in which increased fetal hemoglobin (hemoglobin F, HbF) production continues well into adulthood, disregarding the normal shutoff point after which only adult-type hemoglobin should be produced.
Presentation
The condition is asymptomatic, and is only noticed when screening for other hemoglobin disorders. [Source: Wikipedia 
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