Alpha Thalassemia - StatPearls - NCBI Bookshelf

The .gov means it's official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you're on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation Bookshelf Search databaseBooksAll DatabasesAssemblyBiocollectionsBioProjectBioSampleBooksClinVarConserved DomainsdbGaPdbVarGeneGenomeGEO DataSetsGEO ProfilesGTRIdentical Protein GroupsMedGenMeSHNLM CatalogNucleotideOMIMPMCProteinProtein ClustersProtein Family ModelsPubChem BioAssayPubChem CompoundPubChem SubstancePubMedSNPSRAStructureTaxonomyToolKitToolKitAllToolKitBookghSearch termSearch

• Browse Titles
• Advanced
• Help
• Disclaimer

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-.

StatPearls [Internet].

Show detailsTreasure Island (FL): StatPearls Publishing; 2025 Jan-.Search term Alpha Thalassemia

Janine Harewood; Alexandre M. Azevedo.

Author Information and Affiliations

Authors

Janine Harewood; Alexandre M. Azevedo1.

Affiliations

1 Hospital Santa Marcelina

Last Update: September 4, 2023.

Continuing Education Activity

Hemoglobin H disease (alpha-thalassemia) can be found in patients that live in areas with a high incidence of malaria. Symptoms at presentation, such as episodic anemia, and appropriate diagnostic testing, such as hematology studies and electrophoresis, are essential to timely and proper treatment. This activity reviews the evaluation and management of hemoglobin H disease and highlights the role of the interprofessional team in the recognition and management of this condition.

Objectives:

• Explain the pathophysiology of alpha-thalassemia.
• Explain the typical history and physical examinations in patients with alpha-thalassemia.
• Outline management options for patients with alpha-thalassemia.
• Explain the importance of improving care coordination amongst the interprofessional team to enhance the delivery of care for patients with alpha-thalassemia.

Access free multiple choice questions on this topic.

Introduction

Hemoglobin is made of iron (heme) and protein (globin). The function of hemoglobin is to carry oxygen from the lung to tissues. There are three main types of normal hemoglobin found in adults: Hemoglobin A, hemoglobin A2, and hemoglobin F are the types of globin molecule combinations, namely alpha, beta, gamma, or delta, determine the type of hemoglobin. All of the normal hemoglobin is a combination of alpha and non-alpha chains. The gene for alpha globin is located on chromosome 16. Hemoglobin A is composed of one pair of alpha-globin chains and one pair of beta-globin chains. It makes 95% to 98% of adult hemoglobin. Hemoglobin A2 is a pair of alpha chains and a pair of delta chains. It makes 1% to 3% of adult hemoglobin. Hemoglobin F is comprised of two alpha and two gamma chains. It makes up for the majority of neonatal hemoglobin, but in normal adults is 2% to 3% of the total hemoglobin. The percentages fluctuate based on age, genetics, medications, and underlying conditions.[1][2][3]

Thalassemias are a group of disorders caused by abnormal production of globin chains. The production can be diminished or can be absent for one or more of the globin chains. This imbalance of globin chain production impairs the production of normal hemoglobin. This impairment causes ineffective erythropoiesis with intramedullary hemolysis. Alpha thalassemia refers specifically to the abnormal or absent manufacturing of alpha-globin chains. These are associated with more than 15 different genetic mutations. The severity of the clinical condition is based on the mutation type. The severity of mutation is based on which of the two alpha-globin loci is affected. Mutations can also be deletion or non-deletion. In deletion mutation, there is an inheritance of a single alpha-globin gene. With the non-deletion type, a patient has inherited two alpha-globin genes, but one gene carries a non-deletion abnormality, for example, point mutation. In non-deletion, the severity of clinical expression is also affected depending on whether the mutation blocks the production of the remaining normal alpha chains partially or fully. Hemoglobin H disease occurs when only one normal alpha gene has been inherited. One of these most common non-deletion subtypes of Hemoglobin H is called Hemoglobin Constant Spring. HbH disease tends to be more severe in patients with the non-deletion-type likely due to interference with the transcription of the normal alpha chain gene by the abnormal one.

Etiology

Hemoglobin H forms when only one normal alpha gene has been inherited. This causes significantly impaired alpha globin production. In the neonatal period, this will cause an excess of gamma, and in adults, this leaves an excess of beta-globin chains. Free alpha chains are insoluble. Both gamma and beta chains are soluble and make homotetramers. Hemoglobin H is made of four beta chains, and HbBarts is made of four gamma chains. They are, however, unstable and some precipitate within the cell, leading to a variety of clinical manifestations. HbH in adults can make up to 40% of circulating hemoglobin in affected individuals. This hemoglobin is more susceptible to oxidant injury and has poor oxygen-carrying capacity. Its affinity is ten times more than HbA. It has an abnormal oxyhemoglobin dissociation curve. This means that it can bind to oxygen, but does not deliver it to tissues normally.

Epidemiology

Alpha thalassemia traits are thought to be protective against malaria, and in populations with high incidences of malaria, the trait can be found in up to 90% of the population. Hemoglobin H is similar and found mostly in warm climates. The populations with the highest incidences are found in Southeast Asia, the Mediterranean, and the Middle East. Hemoglobin Constant Spring is the most common form of non-deletion alpha thalassemia. One percent to 2% of individuals living in northeastern Thailand, 5% to 8% of individuals in southern China, and one-quarter of women in an ethnic minority population in Vietnam are found to have Hemoglobin Constant Spring.[4][5]

Pathophysiology

Hemoglobin H can cause chronic hypochromic microcytic anemia and hemolytic anemia, which can worsen in periods of oxidant stress. This can be effectively broken down as ineffective erythropoiesis and increased hemolysis. The microcytic hypochromic anemia is due to impaired hemoglobin production due to decreased alpha chain synthesis and hyperhydration of the cell. The cause of the hyperhydration in alpha thalassemia is not clear. One theory argues that the K-Cl cotransporter stops early, thereby preventing the usual loss of K-Cl and water that is part of the red blood cell remodeling process.

Hemoglobin H has also shown shortened survival down to half of normal, 12 to 19 days versus normal of 28 to 37 days. This has accounted for two main factors: abnormal red blood cell membrane with increased rigidity and increased inclusion bodies. The inclusions were thought to be aggregates of beta chain tetramers, which precipitate in the red blood cell and cause damage, leading to their removal by the spleen. These inclusion bodies are also proposed to cause increased susceptibility to oxidant stress.

History and Physical

HbH disease is classified as moderate to severe in alpha thalassemia. Due to the variety of genetic mutations, as explained previously, there is marked variation in phenotypic expression. Patients can be asymptomatic, have episodic anemia requiring transfusions, and even fatal hydrops fetalis in utero.

Clinical presentation usually starts in the latter part of gestation with hemolytic anemia due to the formation of HbBarts. The most severe form will result in fatal hydrops fetalis. At birth, neonates present with jaundice and anemia.

As they age, patients will have fluctuating degrees of anemia. This anemia is due to a combination of ineffective erythropoiesis and hemolysis. Periods of increased oxidant stress, such as sepsis or certain medications, tend to increase the rate of hemolysis. Patients would then have the typical presentation of hemolytic anemia, indirect hyperbilirubinemia, elevated LDH, decreased haptoglobin, splenomegaly, hepatomegaly, jaundice, variable bony changes, premature biliary tract disease, leg ulcers, and eventually iron overload if multiple transfusions are required without adequate iron chelation.

In adults, the diagnosis is suspected in patients with microcytic anemia with normal iron stores and a normal hemoglobin A2 level on electrophoresis. Hemoglobin levels are usually 8 to 10 g/dL at baseline.

Evaluation

The peripheral blood film in HbH disease shows hypochromia and microcytosis with inclusion bodies. Inclusion bodies are better visualized with a supravital dye such as methyl violet or brilliant cresyl blue. Bone marrow demonstrates erythroid hyperplasia with poorly hemoglobinized erythroblasts carrying inclusion bodies. Hemoglobin electrophoretic or chromatographic techniques can demonstrate HbH. DNA-based genotyping is required for precise diagnosis and is important in prenatal testing and genetic counseling.

Treatment / Management

Supplementation with folic acid should be given because there is hemolytic anemia. HbH patients are at risk of clinical manifestations with oxidative damage. Blood counts should be monitored, and transfusional intervention may be required during periods of oxidant stress, such as infection or oxidant drug use. Patients must be monitored carefully for complications of chronic transfusion and given iron chelation support as needed, especially during the second and third decades of life. Patients require careful genetic counseling.[6][7][8][9]

Differential Diagnosis

The most important differential diagnosis of all the thalassemia syndromes is iron deficiency, which should always be ruled out. Beta thalassemia and combinations of sickle cell disease and thalassemia should also be ruled out.

Consultations

Patients with HbH disease should be followed regularly by a hematologist experienced in the care of hemoglobinopathies and iron overload.

Deterrence and Patient Education

Genetic counseling is mandatory for young patients willing to conceive. Patients should be educated about the consequences of iron overload and the importance of adherence to treatment.

Enhancing Healthcare Team Outcomes

The management of alpha thalassemia is ideally done by an interprofessional team that consists of primary care providers, hematologists, geneticists, nurses, pharmacists, and dietitians. This hemoglobinopathy can affect multiple organs, and close monitoring is required. Supplementation with folic acid should be given because there is hemolytic anemia. Patients with HbH are at risk of clinical manifestations with oxidative damage. Blood counts should be monitored, and transfusional intervention may be required during periods of oxidant stress, such as infection or the use of oxidant drugs. Patients must be monitored carefully for complications of chronic transfusion and given iron chelation support as needed, especially during the second and third decades of life. Patients require careful genetic counseling. Primary care providers should refer patients if transfusions are needed. Pharmacists provide education to patients and monitor compliance. Nurses ensure patient follow up and should notify the team if there are issues. [Level 5]

Review Questions

• Access free multiple choice questions on this topic.
• Click here for a simplified version.
• Comment on this article.

References

1.Chen X, Hu J, Zhu J, Xu W, Yao H, Wu A, Xiao M, Lu Z, Yin L, Fu S. Severe hemolytic anemia due to combined α thalassemia and de novo Hemoglobin Sabine. Ann Hematol. 2019 Mar;98(3):783-785. [PubMed: 30673812]2.Rezende PV, Belisário AR, Oliveira ÉL, Almeida JA, Oliveira LMM, Muniz MBSR, Viana MB. Co-inheritance of a-thalassemia dramatically decreases the risk of acute splenic sequestration in a large cohort of newborns with hemoglobin SC. Haematologica. 2019 Jul;104(7):e281-e283. [PMC free article: PMC6601081] [PubMed: 30630972]3.Zioga A, Thanopoulou E, Hatzi E, Chaliasos N, Georgiou I, Makis A. Rare Association of Hb D-Los Angeles (HBB: c.364G>C) with Hb H Disease: Diagnosis and Clinical Implications. Hemoglobin. 2018 Sep-Nov;42(5-6):336-338. [PubMed: 30626242]4.Byrd KA, Williams TN, Lin A, Pickering AJ, Arnold BF, Arnold CD, Kiprotich M, Dentz HN, Njenga SM, Rao G, Colford JM, Null C, Stewart CP. Sickle Cell and α+-Thalassemia Traits Influence the Association between Ferritin and Hepcidin in Rural Kenyan Children Aged 14-26 Months. J Nutr. 2018 Dec 01;148(12):1903-1910. [PMC free article: PMC6669948] [PubMed: 30517728]5.Zhao P, Wu H, Weng R. Molecular analysis of hemoglobinopathies in a large ethnic Hakka population in southern China. Medicine (Baltimore). 2018 Nov;97(45):e13034. [PMC free article: PMC6250515] [PubMed: 30407298]6.Lal A, Wong TE, Andrews J, Balasa VV, Chung JH, Forester CM, Ikeda AK, Keel SB, Pagano MB, Puthenveetil G, Shah SJ, Yu JC, Vichinsky EP. Transfusion practices and complications in thalassemia. Transfusion. 2018 Dec;58(12):2826-2835. [PubMed: 30260477]7.Brancaleoni V, Di Pierro E, Motta I, Cappellini MD. Laboratory diagnosis of thalassemia. Int J Lab Hematol. 2016 May;38 Suppl 1:32-40. [PubMed: 27183541]8.Lin TF, Huang JN, Cash HL. Investigation of Pediatric Anemia in the Commonwealth of the Northern Mariana Islands. Matern Child Health J. 2019 Mar;23(3):416-421. [PubMed: 30661189]9.Kontomanolis EN, Fasoulakis Z. Hydrops Fetalis and THE Parvovirus B-19. Curr Pediatr Rev. 2018;14(4):239-252. [PubMed: 30124157]

Disclosure: Janine Harewood declares no relevant financial relationships with ineligible companies.

Disclosure: Alexandre Azevedo declares no relevant financial relationships with ineligible companies.

Copyright © 2025, StatPearls Publishing LLC.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

Bookshelf ID: NBK441826PMID: 28722856 Share

Views

• PubReader
• Print View
• Cite this PageHarewood J, Azevedo AM. Alpha Thalassemia. [Updated 2023 Sep 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-.

In this Page

• Continuing Education Activity
• Introduction
• Etiology
• Epidemiology
• Pathophysiology
• History and Physical
• Evaluation
• Treatment / Management
• Differential Diagnosis
• Consultations
• Deterrence and Patient Education
• Enhancing Healthcare Team Outcomes
• Review Questions
• References

Related information

• PMCPubMed Central citations
• PubMedLinks to PubMed

Similar articles in PubMed

• Laboratory Evaluation of Alpha Thalassemia.[StatPearls. 2025]Laboratory Evaluation of Alpha Thalassemia.Motiani A, Zubair M, Sonagra AD. StatPearls. 2025 Jan
• Thalassemia.[StatPearls. 2025]Thalassemia.Bajwa H, Basit H. StatPearls. 2025 Jan
• Review Alpha-Thalassemia.[GeneReviews(®). 1993]Review Alpha-Thalassemia.Tamary H, Dgany O. GeneReviews(®). 1993
• Review Thalassemia: pathophysiology of red cell changes.[Annu Rev Med. 1994]Review Thalassemia: pathophysiology of red cell changes.Schrier SL. Annu Rev Med. 1994; 45:211-8.
• The alpha / beta and alpha 2 / alpha 1-globin mRNA ratios in different forms of alpha-thalassemia.[Biochim Biophys Acta. 1996]The alpha / beta and alpha 2 / alpha 1-globin mRNA ratios in different forms of alpha-thalassemia.Smetanina NS, Leonova JY, Levy N, Huisman TH. Biochim Biophys Acta. 1996 Apr 12; 1315(3):188-92.

See reviews...See all...

Recent Activity

ClearTurn OffTurn On

• Alpha Thalassemia - StatPearlsAlpha Thalassemia - StatPearls

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more... Follow NCBI Twitter Facebook LinkedIn GitHub NCBI Insights Blog

Connect with NLM

• Twitter
• Facebook
• Youtube

National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894

Web Policies FOIA HHS Vulnerability Disclosure

Help Accessibility Careers

• NLM
• NIH
• HHS
• USA.gov