Why are infants with b-thalassemia major not ill until approximately 6 months of age?
a. Infants are protected by their high concentration of Hb F.
b. Infants have less need for hemoglobin because of their small body size.
c. Infants have less need for hemoglobin because of their smaller lung capacity.
d. Infants have a high red count and thus higher hemoglobin from a higher than normal concentration of erythropoietin.
ANS: A
The b globin chain is decreased to absent in b-thalassemia major; however, a globin chain synthesis is normal. Infants up until approximately 6 months of age have an elevated Hb F that does not require b chains. They become symptomatic after the g-to-b switch.
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