Dad 70 yrs old has macrocytic anemia. all else normal. bone marrow biopsy showed no cancer or mds, but failure of production of enough rbc. why?

MDS & Macro Anemia: Causes of macrocytic anemia, other than MDS: vitamin B deficiencies, folate (folic acid) deficiency, certain drugs like zidovudine or hydroxyurea, acute leukemia, LGL leukemia, alcohol abuse, liver disease, hypothyroidism, and lab error. Additional labs include: reticulocyte count, RDW, bilirubin, and others. MDS is difficult to diagnosis and may require next generation DNA sequencing to confirm diagnosis.