A case of megaloblastic pancytopenia with normal mean cell volume

The mean red blood cell volume (MCV) is usually increased in severe megaloblastic anemia. However, in our case a patient presented with pancytopenia and normal MCV was proven to have severe vitamin B12 deficiency. The red blood cell distribution width was markedly increased (three times normal) and led to review of the blood smear and recognition of megaloblastosis as well as prominent red cell fragmentation. This case illustrates that vitamin B12 status should be evaluated in cases of pancytopenia, independent of the MCV value.