Spinal cord compression due to extramedullary hematopoiesis associated with polycythemia vera--case report.

A 69-year-old woman with a 14-year history of polycythemia vera suffered progressive paraparesis due to epidural involvement of hematopoietic tissue. Magnetic resonance (MR) imaging demonstrated extensive epidural masses. Decompressive surgery and radiotherapy were performed and she made an almost complete clinical recovery. Serial MR imaging showed no regrowth of the other epidural masses. Extramedullary hematopoiesis occurs in patients with various hematologic disorders involving a chronic increase in the production of red blood cells, and is often associated with thalassemia, but is less common with polycythemia vera. The most frequent sites are the spleen, liver, and kidney. Extramedullary hematopoietic tissue occurring within the spinal canal and causing cord compression is very rare. Total surgical excision is not usually feasible because of the diffuse nature of extramedullary hematopoietic tissue and the possibility of recurrence, but acute neurological deterioration does require emergency surgery. Extramedullary hematopoiesis is radiosensitive and displays a rapid response to low dosages, so radiation therapy is recommended for residual tumors. Considering the possibility of central nervous system extramedullary hematopoiesis in patients with polycythemia vera, an early diagnosis is necessary for a favorable prognosis.