Paravertebral extramedullary haemopoiesis in a patient with pachydermoperiostosis

Abstract

A 43-year-old white man presented with a history of lower back pain and arthralgia affecting the hands, wrists, knees, ankles and feet. Clinical examination showed pachydermia with coarsening of facial features (top left), palmoplantar hyperhidrosis, digital clubbing, watch-glass nails (bottom left) and a palpable spleen 3 cm below the left costal margin. Laboratory tests showed a high level of C-reactive protein and polyclonal hypergammaglobulinaemia. His blood count and liver, kidney and thyroid function tests were normal, as were rheumatological markers and haemoglobin electrophoresis. Testing for JAK2 V617F was negative. Magnetic resonance imaging revealed a large mass (21.5 9 11.7 9 7.7 cm) with a heterogeneous signal, located in the pre-sacral region, pushing the rectum and bladder anteriorly and extending to the paravertebral area and the epidural space through vertebral foramina (top right). There were paravertebral nodules with similar characteristics in relation to the thoracic and lumbar spine; the spleen measured 14 cm. Biopsy of the mass showed erythroid and myeloid cells and megakaryocytes, indicating extramedullary haemopoiesis (bottom right). The bone marrow was hypocellular (30%), with decreased myeloid precursors and a relative increase in erythroid and lymphoid cells with normal megakaryocytes and no reticulin fibrosis. The overall findings were indicative of pachydermoperiostosis associated with extramedullary haemopoiesis. The patient was treated with prednisone and hydroxycarbamide with control of clinical symptoms and progressive reduction of the mass.