Endocrine Abstracts

Oncogenic osteomalacia (tumor induced osteomalacia-TIO) is a rare disease that can lead to severe physical handicap and pains. Its pathogenesis involves the secretion of fibroblast growth factor-23 inducing urinary phosphate loss and consequent hypophosphataemia. We report a case of a TIO caused by a tumor in the nasal cavity. In 2010, a 61-years-old woman was examined because of muscle weakness and arthralgia in the extremities. Her symptomes started ~3 years before her presentation. He denied any family history of metabolic bone disease. At presentation, she was unable to walk without support. Upon physical examination diminished muscle strength of upper and lower limbs was found without any neurologic alteration. Radiological images, osteodensitometry and technetium-99 m bone scan were characteristic for osteomalacia. Initial laboratory testing revealed a normal serum calcium level, very low phosphate level of 0.46 mmol/l (normal range: 0.84–1.45 mmol/l), an elevated alkaline phosphatase, a normal parathyroid hormone level and slightly decreased 25-hydroxivitamin D. Based on the low serum phosphate levels and her symptoms, the possibility of oncogenic osteomalacia was raised. Chest and abdominal CT was negative. Since the patient reported some episodes of nasal bleeding, an otorhinolaryngological examination was performed. This was revealed a mass in the left nasal cavity. The cranial MRI showed a large soft tissue mass in the left nasal cavity, the sphenoethmoidal recess and the frontal sinus. Given the possibility that this tissue mass was associated with the osteomalacia, it was removed by endoscopic surgery. The histological examination revealed a mesenchymal tumor, myopericytoma. One week later, levels of serum phosphate returned to the normal range, confirming the diagnosis of TIO. At 6-month follow-up, she felt well, she can walk without support and her serum biochemistry is normal.

Conclusion: Tumor induced osteomalacia is mostly associated with mesenchymal tumors that are often occurred in nasal sinuses. Tumor removal - as in our case- may lead to complete recovery.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.