A 40 yo male w polycythemia vera patient was previously typed AB Pos antibody screen negative. He started taking Hydroxyurea to lower his RBC count. A month later his forward typing reaction was:

anti-A = 0

anti-B = mf

anti-D = 4+

control = 0

He has never has any transfusion. My question is how is, what's causing his ABO discrepancy? 

Diseases leading to hematopoiesis stress may influence (i.e. weakening) the A, B, H and I antigens expression (less binding of carbohydrate chains). How is his reverse group?

Sorry. Reverse is his historical AB Pos.

a1 cells = 0

b cells = 0

Also I was reading on the polycythemia vera drug - Hydroxyurea, and it stated that an increase in Hgb F happens when taking it. But if I'm not mistaken, the change in normal Hgb A to Hgb F shouldn't change the RBC surface Ag expression.

To my knowledge no (?).  I believe it is more likely due to his disease leading to this hematopoiesis stress and may have evolved over the time (?). 

1 hour ago, MyHerpesItch said:

Sorry. Reverse is his historical AB Pos.

a1 cells = 0

b cells = 0

Also I was reading on the polycythemia vera drug - Hydroxyurea, and it stated that an increase in Hgb F happens when taking it. But if I'm not mistaken, the change in normal Hgb A to Hgb F shouldn't change the RBC surface Ag expression.

The change in the level of HbF, in itself, shows haematopoietic stress, and haemopoietic stress can lead to weakened expression of ABO antigens.

Thanks ppl for your input. I really appreciate it. 

Well see what happens once the pt is off his meds and the ABO Ag expression comes back. 

Again thank you for your input