Bone Abstracts

Introduction: Tumor-induced osteomalacia (TIO) is a rare acquired paraneoplastic syndrome which is usually induced by mesenchymal tissue tumor with excessive secretion of FGF23. The misdiagnosis of TIO is frequently seen in clinic. Therefore, this study is aimed to describe the misdiagnosed situation of TIO, explore the possible underlying reasons for missed diagnosis and misdiagnosis through the analysis of 144 TIO patients, and improve clinicians’ awareness of TIO.

Methods: The clinical data of 144 surgically treated TIO patients in our hospital during December 1982–December 2014 were retrospectively analysed, including general information, clinical manifestation, laboratory examination, missed diagnosis and misdiagnosis.

Results: 1. General Information. There were 80 male cases (55.6%) and 64 female cases (44.4%), with the onset age being 37.5±11.4 years old. The pathological type was mostly phosphate urinary mesenchymal tumor. After resection of the responsible neoplasm, 117 cases achieved serum phosphorus recovery. 2. The clinical manifestations of TIO mainly included bone pain (99%), difficulty in activity (93%), non-violent fractures (80%), muscle weakness (65%), shorter height (69%), thoracic deformity (33%) and spinal deformity (27%). Bone pain might be the initial symptom (92%). 3. Patients demonstrated low serum phosphorus (0.48±0.13 mmol/l), decreased tubular maximum of phosphate/glomerular filtration rate (TMP/GFR)(0.40±0.17), elevated serum alkaline phosphatase (282.6±161.0 U/l). 4. Missed diagnosis and misdiagnosis analysis. The clinic departments TIO patients referred to mainly distributed in endocrinology (35%), orthopedics (26%), rheumatology (23%), neurology (8%). The misdiagnosis rate was 95%. TIO was frequently misdiagnosed as intervertebral disc herniation (46 case-time), spinal arthritis (including ankylosing spondylitis) (38 case-time), osteoporosis (37 case-time), and other diseases including arthritis, femoral head necrosis, hyperparathyroidism, etc. The missed diagnosis rate of hypophosphatemia was high (43%).

Conclusions: TIO is a vital cause of adult-onset hypophosphatemia in China, but clinicians generally lack awareness and knowledge of this disease. Consequently, the misdiagnosed rate of TIO is high. Therefore, clinicians should further enhance their recognition of TIO and pay attention to searching for tumor in adult-onset patients with hypophosphatemic osteomalacia.