Extramedullary relapse in the left proximal femur with Philadelphia chromosome positive acute lymphoblastic leukemia after allogeneic bone marrow transplantation.

We describe a rare presentation of extra-medullary relapse in an adolescent boy with Philadelphia chromosome-positive acute lymphoblastic leukemia who had undergone allogeneic bone marrow transplantation after first remission. In spite of enduring bone marrow remission, the patient experienced a local relapse in the left proximal femur within 3 years of the transplant. The findings from radiography, bone scintigraphy, and chimerism analysis with short tandem repeats as well as bone marrow aspirates taken via the iliac crests were indeterminate. Magnetic resonance imaging at the onset of hip pain was characterized by decreased signal intensity of the left proximal femur, a finding characteristic of bone marrow edema. Confirmation of extra-medullary relapse of the proximal femur was delayed until histologic proof of the computed tomography-guided biopsy samples was obtained. Overt bone marrow relapse was identified 14 months later. Reestablishment of normal donor hematopoiesis was achieved with reinduction chemotherapy.