Multiple bone fractures of unknown origin

Introduction A 51-year-old patient consulted our ENT ambulance after suffering from multiple bone fractures of unknown origin which began in 2015. In addition, the patient described frequent urination and a weight loss of about 10kg within one year.

Metods In blood examinations one found a hypophosphatemia with a normal but slightly increased renal excretion of phosphate. Vitamin D3 and parathyroid hormone levers were normal.

In a DOTANOC PET-CT, a PET-positive contrast-enhancing lesion of the right ethmoidal cells was detected with no apparent infiltration of surrounding structures.

Endoscopically, a tumor was seen medial of the middle turbinate on the right. While initial biopsy described a spindle celled lesion, further biopsy specimens identified the lesion as a vascular neoplasia. In reference histology, the lesion was compatible to a phosphaturic-mesenchymal tumor and interpreted as a likely cause of hypophosphatemic osteomalacia. Subsequently, the tumor was completely resected via functional endoscopy.

Results After surgery a normalization of the serum phosphate without further phosphate supplementation was shown, and further pathological fractures did not transpire.

Conclusion We present a paraneoplastic osteomalacia as a result of an SSTR-expressing, well-vascularized mesenchymal tumor of the ethmoid. This may be pathophysiologically explained via an overexpression of the fibroblast growth factor FGF-23 with consecutive hypophosphatemia. According to contemporary literature, in the majority of these usually benign lesions, surgical resection results in complete remission of the phosphaturia and resulting sequelae.

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Publication History

Article published online:
07 August 2020