tumor-induced osteomalacia (oncogenic osteomalacia)

Etiology

• secretion of FGF23 by small mesenchymal tumors*

* often difficult to localize

Clinical manifestations

• fatigue, muscle weakness
• osteomalacia: severe bone pain, bone fractures

Laboratory

• FGF23 in plasma elevated
• serum phosphate decreased, urine phosphate increased
• serum alkaline phosphatase is elevated
• 1,25-dihydroxyvitamin D in serum is low
• 25-hydroxyvitamin D in serum is generally normal
• serum PTH, serum calcium generally normal

Radiology

• Dexa scan: reduced bone mineral density

Differential diagnosis

• hypophosphatemic rickets: family history
• secondary hyperparathyroidism: hypocalcemia, serum 25-hydroxyvitamin D low
• Fanconi syndrome: FGF23 in plasma low

Management

• surgical resection resolves symptoms

More general terms

• osteomalacia
• paraneoplastic syndrome