Hemoglobin E#Hemoglobin E/β-thalassaemia

File:Aminoacid chain normal Hb and HbE.pdf

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.

Heterozygous AE occurs when the gene for hemoglobin E is inherited from one parent and the gene for hemoglobin A from the other. This is called hemoglobin E trait, and it is not a disease. People who have hemoglobin E trait (heterozygous) are asymptomatic and their state does not usually result in health problems. They may have a low mean corpuscular volume (MCV) and very abnormal red blood cells (target cells), but clinical relevance is mainly due to the potential for transmitting E or β-thalassemia.{{Citation |last1=Bachir |first1=D |title=Hemoglobin E disease. |date=November 2004 |url=https://www.orpha.net/data/patho/GB/uk-HbE.pdf |access-date=January 13, 2014 |archive-url=https://web.archive.org/web/20160304205359/https://www.orpha.net/data/patho/GB/uk-HbE.pdf |archive-date=March 4, 2016 |url-status=dead |publisher=Orphanet Encyclopedia |last2=Galacteros |first2=F}}

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.{{cite web |last1=Arkansas Department of Health |title=Sickle-Hemoglobin E Disease Fact Sheet |url=https://www.healthy.arkansas.gov/images/uploads/sickle-hemoglobin_e_disease.pdf |access-date=2020-02-28 |archive-date=2020-02-28 |archive-url=https://web.archive.org/web/20200228220925/https://www.healthy.arkansas.gov/images/uploads/sickle-hemoglobin_e_disease.pdf |url-status=dead }}

File:HbE betaThalassemia trait.pdf 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; affecting more than a million people in the world.{{cite journal |author=Vichinsky E |title=Hemoglobin E Syndromes. |journal=Hematology Am Soc Hematol Educ Program |pages=79–83 |year=2007 |pmid=18024613 |doi=10.1182/asheducation-2007.1.79 |volume=2007|s2cid=10435042 |doi-access=free }} Symptoms of hemoglobin E/β-thalassemia vary widely in severity, from mild anemia to full thalassemia major; they can include growth retardation, enlargement of the spleen (splenomegaly) and liver (hepatomegaly), jaundice, bone abnormalities, and cardiovascular problems.{{Cite journal|last1=Fucharoen|first1=Suthat|last2=Weatherall|first2=David J.|date=2012-08-01|title=The Hemoglobin E Thalassemias|journal=Cold Spring Harbor Perspectives in Medicine|language=en|volume=2|issue=8|pages=a011734|doi=10.1101/cshperspect.a011734|issn=2157-1422|pmid=22908199|pmc=3405827}} 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.

File:Red Blood Cell abnormalities.png

Hemoglobin E is most prevalent in mainland Southeast Asia (Thailand, Myanmar, Cambodia, Laos, Vietnam{{Citation | title = Hemoglobin E Trait | publisher = University of Rochester Medical Center | url = http://www.urmc.rochester.edu/Encyclopedia/Content.aspx?ContentTypeID=160&ContentID=12 | access-date = January 13, 2014}}), 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.{{Cite book | url=https://books.google.com/books?id=ywY_dN6ad8gC |title = Populations of the SAARC Countries: Bio-cultural Perspectives|isbn = 9788120725621|last1 = Sarkar|first1 = Jayanta|last2 = Ghosh|first2 = G. C.|year = 2003| publisher=Sterling Publishers Pvt. }}{{cite journal | last=Roychoudhury | first=Arun K. | last2=Nei | first2=Masatoshi | title=Genetic Relationships between Indians and Their Neighboring Populations | journal=Human Heredity | publisher=S. Karger AG | volume=35 | issue=4 | year=1985 | issn=1423-0062 | doi=10.1159/000153545 | pages=201–206}} It is also found at high frequencies in Bangladesh and Indonesia.{{Cite book | url=https://books.google.com/books?id=2grSBwAAQBAJ |title = Genetic Disorders of the Indian Subcontinent|isbn = 9781402022319|last1 = Kumar|first1 = Dhavendra|date = 2012-09-15| publisher=Springer }}{{cite journal|pmc=3237252 | pmid=22089616 | volume=134 | title=Hb E/beta-thalassaemia: a common & clinically diverse disorder | year=2011 | journal=Indian J. Med. Res. | pages=522–31 |vauthors=Olivieri NF, Pakbaz Z, Vichinsky E| issue=4 }} The trait can also appear in people of Turkish, Chinese and Filipino descent. The mutation is estimated to have arisen within the last 5,000 years.{{cite journal |author=Ohashi|title=Extended linkage disequilibrium surrounding the hemoglobin E variant due to malarial selection |journal=Am J Hum Genet |volume=74 |issue=6 |pages=1189–1208 |year=2004 |pmid=15114532 |doi=10.1086/421330 |pmc=1182083|display-authors=etal}} [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1182083/pdf/AJHGv74p1198.pdf Free full text] {{Webarchive|url=https://web.archive.org/web/20230125184006/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1182083/pdf/AJHGv74p1198.pdf |date=2023-01-25 }} 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.{{cite journal |author=Kazazian HH, JR., Waber PG, Boehm CD, Lee JI, Antonarakis SE, Fairbanks VF. |title=Hemoglobin E in Europeans: Further Evidence for Multiple Origins of the βE-Globin Gene. |journal=Am J Hum Genet |volume=36 |issue=1 |pages=212–217 |year=1984 |pmid=6198908 |pmc=1684388}} [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1684388/pdf/ajhg00163-0214.pdf Free full text] {{Webarchive|url=https://web.archive.org/web/20230125184008/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1684388/pdf/ajhg00163-0214.pdf |date=2023-01-25 }}{{cite book| last = Bain | first = Barbara J | title = Blood cells: a practical guide | publisher = Wiley-Blackwell | edition = 4th | date = June 2006 | isbn = 978-1-4051-4265-6}}

A number of studies have shown that the HbE mutation provides a degree of protection against infection with malaria, in common with some other hemoglobinopathies. It is therefore probable that natural selection for the gene may explain why it is most prevalent in parts of the world where malaria has historically been endemic.{{Cite journal |last=Ha |first=Jiwoo |last2=Martinson |first2=Ryan |last3=Iwamoto |first3=Sage K |last4=Nishi |first4=Akihiro |date=2019-01-01 |title=Hemoglobin E, malaria and natural selection |url=https://academic.oup.com/emph/article/2019/1/232/5675503 |journal=Evolution, Medicine, and Public Health |volume=2019 |issue=1 |pages=232–241 |doi=10.1093/emph/eoz034 |issn=2050-6201 |pmc=6925914 |pmid=31890210}}

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• [http://www.doh.wa.gov/Portals/1/Documents/5220/e_trait_pam.pdf Hemoglobin E fact sheet from the Washington State Department of Health]
• [http://asheducationbook.hematologylibrary.org/content/2007/1/79.full American Society of Hematology Educational Program profile of Hemoglobin E disorders]
• [http://www.orpha.net/data/patho/GB/uk-HbE.pdf Orphanet Encyclopedia entry for Hemoglobin E]
• [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1684388/pdf/ajhg00163-0214.pdf Hemoglobin E in Europeans]

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Category:Hemoglobins