Oncogenic osteomalacia presenting as a crippling illness in a young man

Lumbosacral spine MRI in June, 2010, showed ankylosed sacroiliac joints and hip arthritis that were suggestive of ankylosing spondylitis, but non-steroidal anti-inflammatory drugs and disease-modifying antirheumatic drugs gave only modest relief. Oncogenic osteomalacia, an unusual disorder characterised by hypophosphataemia with normal blood calcium, and phosphaturia with normal serum parathyroid hormone from excessive paraneoplastic phosphatonins, was first described by McCance in 1947.2 Most cases are attributable to benign mesenchymal tumours, although giant cell tumours, osteosarcoma, and prostate carcinoma have caused oncogenic osteomalacia.3-5 The disorder is biochemically indistinguishable from inherited forms of hypophosphataemic rickets, so careful family history is essential.