Paravertebral extramedullary haemopoiesis associated with pyruvate kinase deficiency

Abstract

A 62-year-old woman with known pyruvate kinase deficiency and previous splenectomy in early adulthood was investigated for breathlessness. A chest radiograph demonstrated a right retro-cardiac mass and computed tomography/magnetic resonance imaging scans confirmed a 56 · 37 · 60 mm heterogeneous soft tissue mass in the right paravertebral region at the T9/T10 level (top and bottom). The provisional diagnosis was of a neurogenic tumour and surgical excision was planned. Her full blood count at the time was as follows: haemoglobin concentration 101 g/l, white cell count 10AE76 · 10/l, platelet count 660 · 10/l and mean cell volume 105AE9 fl. Bilirubin was 28 lmol/l. She had been transfusion independent. At thoracotomy the mass appeared very vascular and adherent to the ribs and vertebra without bony erosion and with no involvement of nerve roots. The mass was completely excised at thoracotomy and microscopically was composed of varying proportions of mature adipocytes mixed with haemopoietic tissue with normal maturation. Extramedullary haemopoiesis is typically (>90% of cases) found in the liver and spleen in the context of myelofibrosis or thalassaemia but can occur rarely in the paravertebral area, central nervous system, eye, lymph nodes, myocardium, lung and pleura. There have been four previous reports of extramedullary haemopoiesis affecting the paravertebral area associated with pyruvate kinase deficiency with one case leading to spinal cord compression.