October 2001: 40-year-old Xhosa male with back pain and leg weakness

A 40-year-old Xhosa male presented with progressive upper lumbar back pain and weakness At examination he was emaciated and had enlarged lymph nodes in the groin and axilla. Both lower limbs were severely atrophic and weak. Sensation to touch and pain was decreased below L3 bilaterally. MR of the spine showed a discrete, contrast-enhancing epidural mass. A T10-T12 laminectomy revealed an soft, vascular extradural tumor dorsal to the cord. The mass was loosely applied to the dura and easy to remove. The operative specimen consisted of a sausage-shaped (3.5 x 2.0 x 1.2 cm), thinly-encapsulated mass of reddish-brown tissue. The cut surface had a mottled, vaguely nodular, yellowish-brown appearance. Microscopic examination revealed sheets of hematopoeitic elements, including myeloid, red cell and megakaryocytic lines, the latter showing Factor 8-related positivity. The final diagnosis was extramedullary hematopoiesis (EMH). A bone marrow biopsy performed as a result of the diagnosis showed a myeloproliferative disease and polycythemia vera. EMH in the spinal epidural space is a rare but treatable cause of progressive paraparesis in patients with a variety of hematological disorders. Since 1956 there have been more than 50 reported cases, most of which occurred in association with thalassaemia. In spinal cord compression secondary to EMH, the lesions are commonly localized to the mid-lower thoracic region.