Clinical Analysis Of 14 Cases Of Tumor-induced Osteomalacia And Literature Review

Objective: Tumor-induced Osteomalacia(TIO)is a rare paraneoplastic syndrome caused by fibroblast growth factor 23(FGF23)secreting tumors.FGF23 plays an important role in regulating blood phosphorus.TIO is mainly characterized by increased urinary phosphorus excretion and hypophosphatemia.Chronic hypophosphatemia eventually leads to insufficient bone mineralization and clinical manifestations such as bone pain,fatigue and fracture.Tumors are generally benign,and most patients can be cured after complete resection.However,due to the occult onset,atypical clinical manifestations and difficult location of tumor.The misdiagnosed rate of TIO patients is high,and they are often misdiagnosed as arthritis and osteoporosis,thus delay the treatments.In order to improve the understanding,diagnosis and treatment of TIO,we analyzed TIO cases diagnosed in our hospital,and made summary analysis on TIO reported in Chinese population.Methods: 1.The clinical data of14 patients with TIO were retrospectively analyzed over a14-year period(2007.12～2021.08)in Xiangya Hospital Central South University,including clinical manifestations,physical examination,laboratory and imaging examination results.2.TIO case reported in Chinese population were reviewed in literature and was summarize.3.All the cases were divided into two groups:serum phosphorus < 0.5mmol/L and serum phosphorus≥0.5mmol/L,differences in ages,gender,tumor origin,and laboratory results were compared between groups.Results: 1.The onset age of TIO patients was in their 40 s.The vast majority of patients showed bone pain.Pathological fractures could occur in patients with long course of disease.Common laboratory findings were hypophosphatemia,high AKP,low 25(OH)D,high phosphorus clearance and high TPINP.2.Tumors could be found through physical examination in some cases,but most of them were found via.functional imaging combined with anatomical imaging.The tumor prone sites were lower limbs > head and face >trunk > upper limbs > organs.3.The clearance rate of urinary phosphorus in the group with serum phosphorus < 0.5mmol/L was significantly higher than that in the group with serum phosphorus≥ 0.5mmol/L.There was no significant difference in age,sex,blood calcium,AKP,PTH,25(OH)D,β-CTx,TPINP,tumor location and source between the two groups.4.Almost all patients underwent surgery after diagnosis.Most of the postoperative pathology was phosphaturic mesenchymal tumor,and the blood phosphorus increased after operation.Conclusion: 1.TIO is a rare paraneoplastic syndrome with insidious onset,complex diagnosis but curable disease.Patients often present with bone pain and fatigue,and laboratory findings include hypophosphatemia,increased renal phosphate excretion,and elevated AKP.The clearance rate of urinary phosphorus is lower in moderate to severe hypophosphatemia.TIO is easily missed and misdiagnosed due to its atypical symptoms and laboratory findings.2.Somatostatin receptor imaging is of great value for tumor localization.Most of the lesions originate from soft tissues,and the predilection sites of tumors are mostly in the lower extremities,head and face.3.Once the tumor is found,surgical resection is the only curable means.Laboratory indicators such as serum phosphorus should be monitored after surgery,especially for patients with low serum phosphorus after surgery,to be alert to recurrence or metastasis.