Unusual case of acute leukemia. Coexisting acute leukemia and pernicious anemia

Acute nonlymphocytic leukemia developed in a 57-year-old woman following adjuvant therapy with melphalan for ovarian carcinoma. Maturation of differentiating marrow myeloid and erythroid precursors was megaloblastic. The serum vitamin B₁₂ level was low, and Schilling test revealed vitamin B₁₂ malabsorption correctable with intrinsic factor. Megaloblastic maturation of the marrow cells was converted to normoblastic following treatment with vitamin B₁₂ and folic acid. However, blast cells persisted in the marrow, and cytogenetic analysis revealed aneuploidy and trisomy 18. In contrast to the marrow blast cells, there was a decline in circulating blast cells following vitamin replacement, suggesting that these cells were capable of maturation but required vitamin B₁₂ for this purpose.