Hemoglobin E

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Hemoglobin E disease
Other namesHaemoglobin E
Crystal structure of Hemoglobin E mutant (Glu26Lys) PDB entry 1vyt. Alpha chain in pink, beta chain in red. The lysine mutation highlighted as white spheres.
SpecialtyHematology

Hemoglobin E (HbE) is an abnormal hemoglobin with a single point mutation in the β chain. At position 26 there is a change in the amino acid, from glutamic acid to lysine (E26K). Hemoglobin E is very common among people of Southeast Asian, Northeast Indian, Sri Lankan and Bangladeshi descent.[1][2]

The βE mutation affects β-gene expression creating an alternate splicing site in the mRNA at codons 25-27 of the β-globin gene. Through this mechanism, there is a mild deficiency in normal β mRNA and production of small amounts of anomalous β mRNA. The reduced synthesis of β chain may cause

β-thalassemia. Also, this hemoglobin variant has a weak union between α- and β-globin, causing instability when there is a high amount of oxidant.[3] HbE can be detected on electrophoresis
.

Hemoglobin E disease (EE)

First thirty amino acid of normal Hb (on top) and of HbE (down).

Hemoglobin E disease results when the offspring inherits the gene for HbE from both parents. At birth, babies

homozygous for the hemoglobin E allele do not present symptoms because they still have HbF (fetal hemoglobin
). In the first months of life, fetal hemoglobin disappears and the amount of hemoglobin E increases, so the subjects start to have a mild β-thalassemia. Subjects homozygous for the hemoglobin E allele (two abnormal alleles) have a mild hemolytic anemia and mild enlargement of the spleen.

Hemoglobin E trait: heterozygotes for HbE (AE)

target cells), but clinical relevance is mainly due to the potential for transmitting E or β-thalassemia.[4]

Sickle-Hemoglobin E Disease (SE)

Compound heterozygotes with sickle-hemoglobin E disease result when the gene of hemoglobin E is inherited from one parent and the gene for hemoglobin S from the other. As the amount of fetal hemoglobin decreases and hemoglobin S increases, a mild hemolytic anemia appears in the early stage of development. Patients with this disease experience some of the symptoms of sickle cell anemia, including mild-moderate anemia, increased risk of infection, and painful sickling crises.[5]

Hemoglobin E/β-thalassaemia

Heredity of hemoglobin E/β-thalassemia

People who have hemoglobin E/β-thalassemia have inherited one gene for hemoglobin E from one parent and one gene for β-thalassemia from the other parent. Hemoglobin E/β-thalassemia is a severe disease, and it still has no universal cure. However, the mutation is amenable to genome editing at high efficiency in preclinical studies.[6] It affects more than a million people in the world.[7] Symptoms of hemoglobin E/β-thalassemia vary but can include growth retardation, enlargement of the spleen (splenomegaly) and liver (hepatomegaly), jaundice, bone abnormalities, and cardiovascular problems.[8] Recommended course of treatment depends on the nature and severity of the symptoms and may involve close monitoring of hemoglobin levels, folic acid supplements, and potentially regular blood transfusions.[8]

There is a variety of phenotypes depending on the interaction of HbE and α-thalassemia. The presence of the α-thalassemia reduces the amount of HbE usually found in HbE heterozygotes. In other cases, in combination with certain thalassemia mutations, it provides an increased resistance to

P. falciparum).[4] This disease was first described by Virginia Minnich in 1954, who discovered a high prevalence of it in Thailand and initially referred to it as "Mediterranean Anaemia."[8]

Epidemiology

Distribution of red blood cell abnormalities worldwide

Hemoglobin E is most prevalent in mainland Southeast Asia (Thailand, Myanmar, Cambodia, Laos, Vietnam[9]), Sri Lanka, Northeast India and Bangladesh. In mainland Southeast Asia, its prevalence can reach 30 or 40%, and Northeast India, in certain areas it has carrier rates that reach 60% of the population. In Thailand the mutation can reach 50 or 70%, and it is higher in the northeast of the country. In Sri Lanka, it can reach up to 40% and affects those of Sinhalese and Vedda descent.[10][11] It is also found at high frequencies in Bangladesh and Indonesia.[12][13] The trait can also appear in people of Turkish, Chinese and Filipino descent.[1] The mutation is estimated to have arisen within the last 5,000 years.[14] In Europe, there have been found cases of families with hemoglobin E, but in these cases, the mutation differs from the one found in South-East Asia. This means that there may be different origins of the βE mutation.[15][16]

References

  1. ^ a b "Hemoglobin e Trait - Health Encyclopedia - University of Rochester Medical Center".
  2. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2014-06-24. Retrieved 2017-06-08.{{cite web}}: CS1 maint: archived copy as title (link)
  3. PMID 13353880
    .
  4. ^ a b Bachir, D; Galacteros, F (November 2004), Hemoglobin E disease. (PDF), Orphanet Encyclopedia, retrieved January 13, 2014
  5. ^ Arkansas Department of Health. "Sickle-Hemoglobin E Disease Fact Sheet" (PDF).
  6. PMID 37076455
    .
  7. S2CID 10435042
    .
  8. ^
    PMID 22908199
    .
  9. ^ Hemoglobin E Trait, University of Rochester Medical Center, retrieved January 13, 2014
  10. ISBN 9788120725621
    .
  11. ^ http://php.scripts.psu.edu/nxm2/1985%20Publications/1985-roychoudhury-nei.pdf [bare URL PDF]
  12. ISBN 9781402022319
    .
  13. PMID 22089616
    .
  14. PMID 15114532. Free full text
  15. PMID 6198908.{{cite journal}}: CS1 maint: multiple names: authors list (link) Free full text
  16. ISBN 978-1-4051-4265-6
    .

External links
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