Severe osteomalacia with multiple insufficiency fractures secondary to intravenous iron therapy in a patient with Rendu-Osler-Weber syndrome

SUMMARY: This case report describes a 65-year-old man with a Rendu-Osler-Weber syndrome with secondary chronic anaemia, who received multiple intravenous (IV) iron infusions and sustained diffuse bone pain secondary to multiple insufficiency fractures. Laboratory study confirmed fibroblast growth factor 23 (FGF-23)-mediated hypophosphatemia as the main cause of a severe osteomalacia induced by ferric carboxymaltose (FCM). After 3 months or oral phosphate replacement and switching to iron sucrose, serum phosphate levels were normalized and patient improved clinically. INTRODUCTION: Some drugs can induce asymptomatic hypophosphatemia, which if sustained, can lead to a severe osteomalacia with multiple skeletal fractures. This complication has also been described with IV iron therapy. METHODS: This case report describes a patient with Rendu-Osler-Weber syndrome with chronic iron deficiency anaemia, recurrently treated with FCM, who developed a severe osteomalacia with multiple skeletal fractures. RESULTS: Laboratory study showed hypophosphatemia, with high ALP and high FGF-23. Images studies confirmed bone mass loss and multiple insufficiency fractures. A Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18F-FDG PET/CT) did not show hidden tumor, so a diagnosis of FCM-induced hypophosphatemic osteomalacia was performed. Phosphate replacement improved clinical symptoms of the patient. CONCLUSION: Intravenous iron therapy, mainly FCM form, can cause hypophosphatemia, and in some cases induce a severe osteomalacia with multiple fractures, so it seems advisable to monitor serum phosphate levels in high risk patients, as those who receive repeated dose.