To the Editor: Bone marrow necrosis is a rare clinico± pathologic entity most often seen in association with malignancies; rarely, sickle cell disease, infections, or drugs are implicated [1]. The few case reports and small series in the literature quote an incidence of extensive bone marrow necrosis of 0.3 to 12% in various malignant conditions [2±6]. Recovery has been observed following administration of appropriate therapy; the outcome in general depends on the prognosis of the underlying condition.These points are exempli®ed in our experience with a 3-year-old female with acute megakaryoblastic leukemia (FAB M7) in second remission. She developed bone marrow necrosis as a manifestation of relapse after undergoing unrelated peripheral blood stem cell transplantation. We utilized a non-myeloablative (also called immunoablative) conditioning regimen consisting of udaribine, busulfan, and anti-thymocyte globulin because of her impaired cardiac function [7]. Cyclosporine and anti-thymocyte globulin were given as graft vs. host-disease (GVHD) prophylaxis. Neutrophil recovery was achieved on day 15; engraftment was con®rmed with variable N-tandem repeat (VNTR) analysis of peripheral blood by polymerase chain reaction (PCR), which showed 100% donor DNA. The patient developed progressive stage 2 acute GVHD of the skin on day 22 and therapy with methyl prednisolone was initiated. One week later, the patient presented with fever, headache, and body ache. A complete blood count (CBC) showed a white blood cell count of 5.8 Â 10