Anemia which is associated with pancytopenia is

Ref Robbins 9/e p645 The morphologic hallmark of megaloblastic anemia is the presence of megaloblasts, enlarged erythroid precursors that give rise to abnormally large red cells (macrocytes). Granu- locyte precursors are also increased in size. Underlying this cellular gigantism is a defect in DNA synthesis that impairs nuclear maturation and cell division. Because the synthesis of RNA and cytoplasmic elements proceeds at a normal rate and thus outpaces that of the nucleus, the hematopoietic precursors show nuclear-cytoplasmic asynchrony. This maturational derangement contributes to the anemia in several ways. Many megaloblasts are so defective in DNA synthesis that they undergo apoptosis in the marrow (inef- fective hematopoiesis). Others mature into red cells but do so after fewer cell divisions, fuher diminishing the output of red cells. Granulocyte and platelet precursors are also affected (although not as severely) and most patients present with pancytopenia (anemia, thrombocytopenia, and granulocytopenia).