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Old 01-05-2013
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RBC Alpha Thalassemia Concepts

Hi guys,

Can you guys please explain me alpha thalassemias. I have confusion on following points

1. In Asians and blacks there is 2 gene deletion either on same or diff chromosomes. So, the rest of 2 genes are they still capable of producing alpha globins? Is that why Hb electrophoresis is normal but with decreased in Hb and Hct ?


2. In 3 gene deletions (which is called HbH disease) still there is 1 alpha gene remaining is it not capable of producing at least 1 alpha globin? is that why beta chains have replaced 2 alpha chains making total 4 beta chains?

3. In 4 gene deletions (called Hb Bart dz) why not still beta chains replace alpha chains and make it HbH dz? why only gamma chains replace making it Hb Bart ?

Sorry the questions were too long.

thank you

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Old 01-05-2013
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Beta chain production starts postnatally.

Hb Barts is composed of gamma chains only (early fetal life). Since patients are born dead (still birth), they never get a chance to make beta globins.

In Hb H disease. Yes there is still one alpha gene working producing some alpha chains. These few alpha chains will go and make normal Hb A (2 alpha and 2 beta). But because you have an excess of beta chains (unmatched by alpha chains), these beta chains will produce the beta4 tetramer (Hb H).

For your first question. Yes, you got the answer right.

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  #3  
Old 01-06-2013
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thank you step taker.Now my doubts on thalassemias are cleared.ready to face any question on thalassemias
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