Recommended Citation
Cecil A, Shagi M, Haider S, Gardezi SA. Tumor-Induced Osteomalacia: A Case Report and Literature Review. Presented at Scientific Day; May 20, 2026; Milwaukee, WI.
Abstract
Background/Significance:
Tumor-induced osteomalacia (TIO) is an ultra-rare paraneoplastic syndrome caused by excessive fibroblast growth factor 23 (FGF23) secretion from phosphaturic mesenchymal tumors, resulting in hypophosphatemia and osteomalacia. Diagnosis is frequently delayed due to nonspecific symptoms and difficulty localizing small tumors.
Description:
A 55-year-old male presented with 16 months of progressive muscle weakness, multiple bilateral metatarsal fractures, and chronic bone pain. Laboratory evaluation revealed profound hypophosphatemia (1.6 mg/dL), markedly elevated FGF23 (455 RU/mL), and evidence of renal phosphate wasting (TRP 35%, TmP/GFR 1.04 mg/dL). Initial FDG-PET/CT was non-localizing. Upon referral, specialized re-interpretation at a tertiary referral center identified faint focal uptake in the right third metacarpal, subsequently confirmed by technetium-99m sestamibi scanning and MRI, which demonstrated a 1.9 × 1.8 × 1.2 cm soft-tissue mass in the palmar tissues. Surgical excision confirmed a phosphaturic mesenchymal tumor with positive FGF23 in situ hybridization. Serum phosphorus normalized postoperatively, confirming cure.
Discussion:
This case highlights the diagnostic challenges of TIO, particularly the difficulty in localizing the tumor and the critical importance of expert imaging interpretation. Complete surgical resection remains the definitive treatment, with rapid biochemical normalization and symptom improvement. The unusual hand location and initially non-localizing imaging underscore the need for systematic diagnostic approaches and multidisciplinary management in this rare but treatable condition.
Presentation Notes
Presented at Scientific Day; May 20, 2026; Milwaukee, WI.
Full Text of Presentation
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Document Type
Poster
Open Access
Available to all.
Tumor-Induced Osteomalacia: A Case Report and Literature Review
Background/Significance:
Tumor-induced osteomalacia (TIO) is an ultra-rare paraneoplastic syndrome caused by excessive fibroblast growth factor 23 (FGF23) secretion from phosphaturic mesenchymal tumors, resulting in hypophosphatemia and osteomalacia. Diagnosis is frequently delayed due to nonspecific symptoms and difficulty localizing small tumors.
Description:
A 55-year-old male presented with 16 months of progressive muscle weakness, multiple bilateral metatarsal fractures, and chronic bone pain. Laboratory evaluation revealed profound hypophosphatemia (1.6 mg/dL), markedly elevated FGF23 (455 RU/mL), and evidence of renal phosphate wasting (TRP 35%, TmP/GFR 1.04 mg/dL). Initial FDG-PET/CT was non-localizing. Upon referral, specialized re-interpretation at a tertiary referral center identified faint focal uptake in the right third metacarpal, subsequently confirmed by technetium-99m sestamibi scanning and MRI, which demonstrated a 1.9 × 1.8 × 1.2 cm soft-tissue mass in the palmar tissues. Surgical excision confirmed a phosphaturic mesenchymal tumor with positive FGF23 in situ hybridization. Serum phosphorus normalized postoperatively, confirming cure.
Discussion:
This case highlights the diagnostic challenges of TIO, particularly the difficulty in localizing the tumor and the critical importance of expert imaging interpretation. Complete surgical resection remains the definitive treatment, with rapid biochemical normalization and symptom improvement. The unusual hand location and initially non-localizing imaging underscore the need for systematic diagnostic approaches and multidisciplinary management in this rare but treatable condition.
Affiliations
Aurora Sinai Medical Center, Aurora St. Luke's Medical Center