Meningeal hematopoiesis following radiation myelitis in a hematopoietic stem-cell transplant recipient.

Extramedullary meningeal hematopoiesis (EMH) represents an uncommon finding after stem-cell transplantation. We describe the case of an allogeneic bone marrow transplantation (BMT) recipient who developed EMH 1 month after radiation myelitis had been diagnosed. A 39-year-old man with multiple myeloma underwent matched unrelated BMT following a myeloablative conditioning regimen of cyclophosphamide and total-body irradiation (200 cGyx6). This was followed by delivery of 40 Gy of involved-field radiation to an extramedullary plasmacytoma compressing the spinal cord. Although transplantation went extremely well, the patient developed radiation myelitis 7 months after transplantation, and EMH ensued 1 month later. Because the patient was not in a disease state known to cause EMH, it is tempting to speculate that radiation-related neural injuries might cause donor cells to migrate to the central nervous system.