B-Thalessemia trait what is elevated? -

the increase in HbA2 is diagnostically useful, paicularly in induviduals who are at risk for both B thalassemia trait and iron deficiency. Two mechanisms contribute to the anemia in b-thalassemia. The reduced synthesis of b-globin leads to inadequate HbA formation and results in the production of poorly hemoglobinized red cells that are pale (hypochro- mic) and small in size (microcytic). Even more impoant is the imbalance in b-globin and a-globin chain syn- thesis, as this creates an excess of unpaired a chains that aggregate into insoluble precipitates, which bind and severely damage the membranes of both red cells and erythroid pre- cursors. A high fraction of the damaged erythroid precursors die by apoptosis (Fig. 11-6), a phenomenon termed ineffec- tive erythropoiesis, and the few red cells that are produced have a shoened life span due to extravascular hemoly- sis. Ineffective hematopoiesis has another untoward effect: It is associated with an inappropriate increase in the absorption of dietary iron, which without medical intervention inevitably leads to iron overload. The increased iron absorption is caused by inappropriately low levels of hepcidin, which is a negative regulator of iron absorption (see later). Ref: Robbins pathologic basis of disease 9/e . Pg:641