Case Study Answer

QUESTION: How do these two patients with ITP differ?

ANSWER: One has thalassemia trait, the other has iron deficiency anemia (from chronic GI blood loss secondary to his thrombocytopenia). I did not provide the Hb/Hct, but the latter can be calculated by multiplying MCV x RBC count. Note how the patient with thalassemia trait can compensate for the small size of the RBC by making many more red cells (increased RBC count), thus achieving an optimal Hb/Hct. The patient with IDA would surely like to compensate for his small RBC size, but because he is missing a critical nutrient (iron), erythropoiesis is suppressed, leading to inappropriately low RBC count, and Hb/Hct. All this is formalized by the Mentzer index.