[Oncogenic osteomalacia in a 49-year-old female patient]

A 49-year-old woman presented with increased bone and muscle pain of the left thigh and also of the left ribs since 1 1/2 year. 2 osteolytic regions on the left proximal femur were punctured but no tumour-like changes were found.

Laboratory tests showed a severe hypophosphataemia (0.33 mmol/l), increased serum alkaline phosphatase activity and moderate elevated parathyroid hormone. Renal loss of phosphate was measured under phosphate substitution. The bone mineral density (DXA) was decreased. With octreotid scintigraphy a somatostatine receptor positive tumour was detected on the right proximal thigh and magnetic resonance scanning confirmed localization of the tumour.

Treatment with oral phosphate and calcitriol improved the complaints presently. After total removal of a mesenchymal tumour, normalization of serum phosphate occurred and the patient did not require any medicine and did not have complaints anymore.

In a case of uncertain hypophosphataemic osteomalacia in adults it is essential to search for a tumour after exclusion of the rare differential diagnoses to enable a causal treatment of a potentially oncogenic osteomalacia.