Oncogenic osteomalacia should be considered in hypophosphatemia, bone pain and pathological fractures.

The clinical manifestation of oncogenic osteomalacia includes bone pain, pathological fractures, general fatigue and muscle weakness. Such unspecific symptoms hinder the establishment of a proper diagnosis which very often requires long-lasting investigations with many diagnostic imaging methods. Here, we discuss difficulties in the diagnosis of oncogenic osteomalacia using the example of our own clinical case: a 56 year-old woman with a history of pain in the left hip and two years of walking difficulties. A plain radiograph and CT scan revealed pathological fractures. Multiple myeloma, primary hyperparathyroidism and bone metastatic disease were excluded. Routine laboratory tests showed elevated alkaline phosphatase and a mild degree of hypophosphatemia. CT and MR imaging confirmed the presence of a pathological mass in the thorax. Tumour excision and histopathological test results revealed the diagnosis of a phosphaturic mesenchymal tumour. Our case, showing the clinical course of the disease from the symptoms manifested at the beginning to the establishment of the diagnosis, can serve as a model illustration of the diagnostic struggle involved with oncogenic osteomalacia.