Kalfa and colleagues previously found that mice deficient in Rac1 and Rac2 (Rac1−/−Rac2−/− mice) exhibited mild microcytic anemia with significant anisocytosis, poikilocytosis, polychromasia, and increased hypochromic cells, target cells, and fragmented erythrocytes [3], [5]. This evidence concerns the gene RAC1 and microcytic anemia.