Osteomalacia Following Iron Infusion Therapy in a Patient With Rendu-Osler-Weber Syndrome: F-18-FDG PET/CT Discrimination of a Stress Fracture in the Setting of a Musculoskeletal Tumor Mimic.

This case report highlights a rare occurrence of osteomalacia induced by hypophosphatemia secondary to ferric carboxymaltose (FCM) therapy in a patient with hereditary hemorrhagic telangiectasia (HHT, or Rendu-Osler-Weber syndrome). A 21-year-old man presented with left tibial pain without prior trauma, accompanied by severe hypophosphatemia, vitamin D deficiency, and elevated fibroblast growth factor 23 (FGF23) levels. Upon the full diagnostic imaging work-up, F-18-FDG PET/CT majorly contributed to the differential diagnosis by excluding potential malignancy and verifying a stress fracture. Treatment included vitamin D supplementation and oral phosphorus replacement, along with discontinuation of ferric carboxymaltose (FCM) therapy. This case demonstrates the importance of vigilance for metabolic bone disease in patients undergoing FCM treatment, particularly those with predisposing conditions such as HHT, to prevent misdiagnosis and mitigate complications.