Paraplegia due to a paravertebral extramedullary haemopoiesis in a patient with polycythaemia vera.

In July 1985, a 43-year-old man was found to have polycythaemia vera. The peripheral blood counts were white cell count 14.15x109/l (neutrophils 80%, lymphocytes 14%, monocytes 5%, eosinophils 1%), haemoglobin concentration 24.8 g/dl, haematocrit 0.7, red cell count 8.15x1012/l (neither anisocytosis nor poikilocytosis nor tear-drop poikilocytosis were observed), platelets 234x109/l. As only the erythroid lineage was affected significantly, he was treated with isovolaemic phlebotomy until April 2004. In May 2004, the patient suddenly developed a spastic paraplegia. Nuclear magnetic resonance imaging showed a posterior extradural tumour extending from T3 to T11 (fig 1A, B). The lesion expanded into the vertebral canal, inducing spinal cord compression. The occurrence of either a second neoplasm or a myeloid sarcoma (rare but possible during the clinical course of polycythaemia vera) was considered in the differential diagnosis. After thoracic laminectomy (from T2 to T11) and . . .