Asian Journal of Orthopaedic Research

One of the rare paraneoplastic syndrome of osteomalacia is oncogenic osteomalacia or tumor induced osteomalacia (TIO) where there is phosphate depletion and abnormal vitamin metabolism caused due to small endocrine tumor that secrets phosphaturic hormone, fibroblast growth factor [1]. Phosphaturic mesenchymal tumour is very uncommon and is very difficult to diagnose. Usually it is misdiagnosed as other mesenchymal tumour due to its heterogenecity [1]. There is inappropriate FGF-23 secretion which causes low phosphate and 1,25-dihydroxyvitamin D levels [2,3].

We are going to present a case of hypophosphatemic rickets secondary to phosphaturic mesenchymal tumour who came with complaints of proximal muscle weakness which limited his effort tolerance and activities of daily life like standing from squatting position and rib pain. His FGF-23 levels were very high above normal levels and PET CT revealed a well-defined enhancing lesion abutting femoral neurovascular bundle. After consultation with endocrinologist we have d done complete excision of the mass. Post surgery all symptoms were relieved, proximal muscle strength improved gradually and serum levels of phosphorus, ALP and FGF-23 came back to normal.