This site is intended for healthcare professionals

Go to /sign-in page

You can view 5 more pages before signing in

Alpha thalassaemia

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Alpha thalassaemia is the result of defective production of the alpha chain of haemoglobin. It is mainly found in the Far East, Middle East and Africa.

The normal alpha genotype is written alpha alpha/ alpha alpha as two alpha globin genes are inherited from each parent.

Unlike β thalassaemia where no-deletion mutations predominate, in α thalassaemia there is deletion of 1 or both a-globin genes from chromosome 16 (1).

  • Deletion of one alpha globin genes of one of the chromosome pairs produces the haematologically silent carrier state - genotype - alpha/ alpha alpha.
  • Deletion of two alpha globin genes produces the alpha thalassaemia trait. This is associated with mild hypochromic anaemia and may result from either
    • loss of both pairs of genes from one chromosome - giving a --/alpha alpha genotype. This is most prevalent among Asians especially in S.E. Asia
    • loss of one gene from each chromosome - giving a - alpha/- alpha genotype. This is most prevalent among black Africans.

  • Deletion of three alpha globin genes results in Haemoglobin H disease with a genotype of --/- alpha. Alpha chain synthesis is severely suppressed so that unstable tetramers of excess beta globin - HbH - are formed. Clinically, it resembles beta thalassaemia intermedia.
  • Deletion of all four alpha globin genes produces haemoglobin Bart's Hydrops syndromes - genotype --/--. It is incompatible with life, foetal death occurring at about 38 weeks
  • The haplotype --/ (i.e. one chromosome pair having both alpha globin genes deleted) is known as alpha 0.
  • The haplotype -alpha/ (i.e. one chromosome pair having a single alpha globin gene deleted) is known as alpha+

Reference:

  1. Piel FB, Weatherall DJ. The alpha-thalassemias. N Engl J Med. 2014 Nov 13;371(20):1908-16

Create an account to add page annotations

Annotations allow you to add information to this page that would be handy to have on hand during a consultation. E.g. a website or number. This information will always show when you visit this page.

The content herein is provided for informational purposes and does not replace the need to apply professional clinical judgement when diagnosing or treating any medical condition. A licensed medical practitioner should be consulted for diagnosis and treatment of any and all medical conditions.

Connect

Copyright 2024 Oxbridge Solutions Limited, a subsidiary of OmniaMed Communications Limited. All rights reserved. Any distribution or duplication of the information contained herein is strictly prohibited. Oxbridge Solutions receives funding from advertising but maintains editorial independence.