An uncommon cause of polyarthralgia

Tumour induced osteomalacia (TIO) is a paraneoplastic syndrome characterized by renal phosphate wasting and hypophosphatemic osteomalacia, caused by FGF-23 (Fibroblast growth factor-23) producing mesenchymal tumours. Here, we report the case of a 40 year old lady referred by her family physician for multiple joint pains of 2 years duration. There was no evidence of inflammatory arthritis. Biochemical investigations revealed low phosphorus, with raised alkaline phosphatase and high levels of FGF-23. As a TIO was considered likely, functional imaging with a DOTATATE PET scan was done, which revealed a DOTA avid lesion in the right foot. Following surgical excision of the tumour, there was significant relief in symptoms and gradual recovery of phosphate to normal levels. It is relevant and important for family physicians as in subjects with symptom like polyarthralgia, a simple measurement of analytes like phosphate, calcium and alkaline phosphatase in primary care setting will help to arrive at a cause and referral for further evaluation as this condition is potentially treatable.