Madibular Phosphaturic Mesenchymal Tumor Induced Osteomalacia: 2 Cases

TIO is a rare disorder with currently undefined incidence. PMTs represent the predominant etiology. The insidious disease onset and diagnostic challenges frequently result in misdiagnosis and delayed treatment. We report two cases of mandibular PMT-induced osteomalacia: 1.A 25-year-old male presented with severe hypophosphatemia (0.41 mmol/L), diffuse arthralgia, and proximal myopathy;2.A 49-year-old female demonstrated 3-year progressive lower limb weakness culminating in bilateral fractures with persistent hypophosphatemia. DOTATATE PET-CT localized mandibular tumors in both cases, with complete symptomatic resolution following surgical excision. Tumor-induced osteomalacia (TIO), though rare, poses significant diagnostic challenges, frequently delaying treatment. These cases highlight the necessity of suspecting TIO in unexplained osteomalacia with hypophosphatemia. Current epidemiological data remain limited. Key features of TIO include: Profound hypophosphatemia (serum phosphorus: 0.41 ± 0.13 mmol/L; normal: 0.85–1.51) FGF23 overexpression, disrupting phosphorus metabolism DOTATATE PET-CT for tumor localization and surgical planning TIO is one of the important causes of adult-onset hypophosphatemic osteomalacia. The awareness of the disease could avoid the delay on diagnosis in clinical.