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Tumour-Induced Osteomalacia FGF23 — ESENeph MCQ

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HardElectrolyte DisordersTumour-Induced Osteomalacia FGF23ESENeph

A 55-year-old man develops tumour-induced osteomalacia (TIO). He has severe hypophosphataemia (phosphate 0.3 mmol/L), elevated FGF23, low 1,25-dihydroxyvitamin D, and bone pain with fractures. An FGF23-producing mesenchymal tumour is localised on octreotide PET-CT. What is the definitive treatment?

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Correct answer: A — Surgical excision of the FGF23-producing tumour

Tumour-induced osteomalacia (TIO) is caused by mesenchymal tumours that secrete FGF23, causing renal phosphate wasting, hypophosphataemia, and impaired 1,25-dihydroxyvitamin D synthesis. This leads to osteomalacia. The definitive treatment is surgical excision of the tumour, which is curative – FGF23 levels normalise and phosphate recovers within days. If the tumour cannot be located or is unresectable, medical management with phosphate supplements and calcitriol is used. Burosumab (anti-FGF23 antibody) is being investigated for unresectable TIO.

Reference: https://guidelines.ukkidney.org