Bone marrow aplasia with prominent atypical plasmacytic proliferation preceding acute lymphoblastic leukemia

A two-year-old boy presented with pancytopenia. Bone marrow examination revealed an aplastic marrow with prominent immature plasma cell proliferation, which mimicked plasma cell leukemia. Immunohistochemistry, however, revealed a polyclonal population consistent with a reactive process, excluding plasma cell neoplasia. Administration of granulocyte-colony stimulating factor resulted in recovery of normal hematopoiesis with resolution of plasmacytosis. Seven months later, the patient had an elevated white blood cell count and bone marrow findings diagnostic of acute lymphoblastic leukemia. To the best of our knowledge this is the first reported case of bone marrow aplasia with prominent polyclonal plasmacytosis presenting as a prodrome of acute lymphoblastic leukemia in childhood.