Anemia

Abstract

The differential diagnosis of anemia is made easier by classifying RBC morphology as (1) hypochromic and microcytic, (2) normochromic and normocytic, and (3) macrocytic. This limits the number of diagnostic considerations and, hence, limits the laboratory evaluation. There are relatively few considerations if the RBCs are hypochromic and microcytic, including iron deficiency and the thalassemia syndromes. If the RBCs are normochromic, the reticulocyte percentage indicates whether the bone marrow is providing an appropriate response for the degree of anemia. There also are few possibilities if the reticulocyte percentage is low, ie, Diamond-Blackfan syndrome and transient erythroblastopenia of childhood. In the absence of bleeding, a brisk reticulocyte response indicates hemolysis due either to an intrinsic (congenital) or to extrinsic (acquired) RBC defect. The patient's history and physical examination findings may provide additional clues, and RBC features such as irreversibly sickled cells or spherocytes may indicate a specific diagnosis. Finally, the macrocytic anemias are suggested when the MCV exceeds 100 fL per cell and there are macroovalocytes on the blood smear. Such findings warrant further exploration of vitamin B12 and folic acid deficiency syndromes.