Ineffective erythropoiesis is a well-known phenomenon that occurs in patients with vitamin B12 deficiency. The mechanism that leads to this phenomenon involves defective DNA synthesis with megaloblastic transformation of bone marrow and intramedullary hemolysis. Although intense erythroid hyperplasia occurs, the erythroid cells do not mature normally and subsequently die in the bone marrow. Markers of hemolytic anemia (eg, elevated lactate dehydrogenase, low haptoglobin, indirect hyperbilirubinemia) may become evident, but reticulocyte response is typically absent in such patients.
