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Q. What is the reason for increased RBC count when 2 genes are deleted in alpha-thalassemia? Since thalassemia is a problem in globin chain synthesis, Hb can't be formed and thus anemia occurs. How is it possible that Hb is decreased but RBC count is increased ? I was thinking they hold the proportional relationship but here it's not so. Can anybody pls help to keep these things straight.Thanks.
 

Crayola227

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Hb and RBC are two different concepts.

Hemoglobin is the protein created and stuffed inside each individual RBC.

Anemia can be either decrease in number of RBCs, or concentration of Hemoglobin in RBCs, or both. Either mechanism leads to decrease in oxygen carrying capacity of blood.

Remember, thalassemia can be mutation or deletion of the alpha or beta chain, it could be 2 alpha genes, 2 beta genes, or mixed one alpha and one beta. You can still produce hemoglobin in alpha or beta thalassemia, but the person will either only have the one chain to do so rather than use both chain types, and the resultant hemoglobin is not as good.

I'm not explaining this terribly well, why not look this up?

But yes, actually, RBC count increase can actually lead to decreased hemoglobin concentration within each RBC if essentially the production of RBCs is outpacing the precursors needed to make enough hemoglobin to keep a proper concentration within each.

Conversely, you could have a low RBC count but normal hemglobin concentration within each.

I'm not sure if an elevated RBC count in thalassemia could represent a normal compensation for the issue or if it suggests there is some other issue at work.

Try reading uptodate if you have access for a better discussion than what I've given you.

Bottom line is to understand all the values in a CBC are in fact distinct measures, although often an effect on one can be reflected in another, they are not merely proportionally related nor exactly the same or substitutable. You hear hemoglobin and crit used interchangeably, and that's usually fine, but know that they represent different measures, and they are cases where they don't line up as expected and this is a clue. This is why all the measures exist and are reported, interpreted all together can represent differing pathologies in different combinations.

As a physician, you will need to know how to interpret these studies, and know when to order further tests. That's beyond me explaining here but I wanted to throw out that don't forget the value and having the order for a peripheral smear in your backpocket, it can provide valuable info you wouldn't get from the numbers you get from most other blood tests.

Hope this helps a bit.
 

Entadus

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To put it simply, the body realizes there's hypoxia due to the anemia (low oxygen carrying capacity). The kidney releases EPO to stimulate the bone marrow to produce more Erythrocytes. There is increased hematopoiesis with increased reticulocyte count (even though the newly formed RBC's will be defective due to low HbA along with the presence of HbH (tetramers of B-globin)
 
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Thanks cyayola227 and Entadus for clearing my confusions.They helped a lot.
 
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OP
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May 25, 2015
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One more related question made me scratch my head.

In both Goljan & pathoma, there is mention of increased RBC count only in B-thalassemia minor and alpha-thalassemia when 2 genes are deleted. Won't there by increased RBC count in B-thalassema major and if 3 or 4 genes are deleted in alpha-thalassemia? Why RBC count is increased in some conditions and not in others ( since rest of the other conditions causes even more severe anemia so that bone marrow production of RBC should increase even more, isn't it so)?.Pls share your knowledge and understanding on this.Thanks .
 
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Entadus

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You will likely see increased reticulocyte count with Thal-major, which is an indication that the bone marrow has increased hematopoiesis in response to the anemia. I don't think there would be an actual increase in the erythrocyte (RBC) count, though.

Remember that there would be increased destruction of the RBC's in the spleen since the macrophages recognize abnormal precipitates of hemoglobin (tetramers of alpha-globin)

EDIT: In Beta Thalassemia major, the anemia can be so bad that the hematopoietic response can be greatly expanded ("massive erythroid hyperplasia"). In other words, hematopoiesis can occur outside of the bone marrow, especially in the bones of the skull/face. This leads to the "crew cut" appearance on head X-ray along with "chipmunk" facies. Again, this is just a compensatory mechanism that TRIES to get the RBC count and Hemoglobin level back to normal... however there will still be a profound hypo-chromatic microcytic anemia with low hematocrit, low Hgb, and abnormal cells (target cells, schistocytes) seen on smear
 
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