Decreased red blood cell (RBC) production Defects in RBC production may be Congenital Acquired Congenital defects are extremely rare, but the most common are Diamond-Blackfan anemia Fanconi anemia Diamond-Blackfan anemia is characterized by lack of RBC precursors in bone marrow, macrocytic RBCs, lack of reticulocytes in peripheral blood, and lack of involvement of other blood cell lineages.