Hereditary persistence of fetal hemoglobin (HPFH) is a benign condition in which increased

fetal hemoglobin Fetal hemoglobin, or foetal haemoglobin (also hemoglobin F, HbF, or α2γ2) is the main oxygen carrier protein in the human fetus. HemoglobinF is found in fetal red blood cells, and is involved in transporting oxygen from the mother's bloodstream ...

( hemoglobin F, HbF) production continues well into adulthood, disregarding the normal shutoff point after which only adult-type

hemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...

should be produced.

Presentation

The condition is asymptomatic, and is only noticed when screening for other hemoglobin disorders.

Sickle cell disease

In persons with sickle cell disease, high levels of fetal hemoglobin as found in a newborn or as found abnormally in persons with hereditary persistence of fetal hemoglobin, the HbF causes the sickle cell disease to be less severe. In essence the HbF inhibits polymerization of HbS. A similar mechanism occurs with persons who have sickle cell ''trait''. Approximately 40% of the hemoglobin is in the HbS form while the rest is in normal HbA form. The HbA form interferes with HbS polymerization.

Causes

HPFH can be caused by

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...

s in the ''β'' globin gene cluster, or the γ gene promoter region. In addition HbF levels are influenced by polymorphisms in the BCL11A gene and in the MYB gene enhancer. In HPFH the percentage of HbF varies from 0.8-1.0% to about 30% of the total hemoglobin, but levels as high as 100% can be seen in homozygotes for delta beta thalassemia.

Diagnosis

Epidemiology

About 10% of the population has an HbF level >1.0%. HPFH may alleviate the severity of certain hemoglobinopathies and

thalassemia Thalassemias are a group of Genetic disorder, inherited blood disorders that manifest as the production of reduced hemoglobin. Symptoms depend on the type of thalassemia and can vary from none to severe, including death. Often there is mild to ...

s, and is selected for in populations with a high prevalence of these conditions (which in turn are often selected for in areas where

malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...

is endemic). Thus, it has been found to affect people of African and Greek descent.

References

External links

{{Diseases of RBCs Hereditary hemolytic anemias Disorders of globin and globulin proteins