Part â… :Clinical Spectrum Of X-Linked Hypophosphatemia In Adults Part â…¡:Genetic Fusion Of Phosphaturic MesenchymalTumors

BackgroundX-linked hypophosphatemic rickets (XLH) is the most common type of inherited hypophosphatemic rickets, characterized by disorder of phosphate homeostasis and inherited in an autosomal dominant trait. This disease arises from inactivating mutations in phosphate regulating gene with homologies to endopeptidases on the X chromosome (PHEX). Loss-of-function mutations of PHEX can lead to elevated fibroblast growth factor 23 (FGF23), the main factor that reduce renal tubular reabsorption of phosphate, resulting in impaired skeletal mineralization. Clinical manifestations of XLH demonstrate a great range of severity associated with an earlier age of onset. The most common symptoms noted in the early stage were known well. The hypophosphatemia and mineralization defect of XLH persists in adulthood, manifests as osteomalacia. However, much of what is understood about the manifestations of adult XLH has been derived from familial kindred and case reports, lacking systematical assessment on adult stage for the natural course and prognosis of the disease. Therefore, this study systematically assessed the clinical, biochemical and radiological features of XLH patients.Objective1. Systematically described anthropometric, clinical, biochemical and radiological features in genetically verified adult patients with XLH.2. Assess the musculoskeletal complications in XLH patients using standardized radiographic methods and definitions.Methods1. Subjects:This cross-sectional study of adult XLH was performed at PUMCH during 2013-2015. Patients 18 years of age and older were recruited during clinical follow-up or upon screening of first degree relatives of XLH child.2. Methods:(1) Clinical data:we collected the clinical data including general information, sign, clinical symptoms, anthropometric measurements, previous and current treatment from questionnaire survey.(2) Biochemical and bone turnover markers:Fasted whole blood samples were collected and placed at 4 ℃ for less than 30 mins and separate the serum for analysis. All routine laboratory studies on serum and urine were performed according to routine assays available in central laboratory. Serum intact FGF23 were measured by two-site enzyme-linked immune sorbent assay (ELISA). Serum 25-hydroxyvitamin D (25(OH)D), Procollagen 1 N-terminal Peptide (P1NP), osteocalcin and intact PTH (iPTH) concentration were determined by automated electrochemiluminescence system.(3)BMD, X-ray film and pQCT:Bone mineral density (BMD) of the lumbar spine1-4 (L1-4) and the right femoral neck were detected by dual energy X-ray absorptiometry (DXA), Plain X-ray of the pelvis, knees, left heel, lateral thoracolumbar spine was performed to detect osteomalacia characters, and osteoarthritis, as well as enthesopathy. The pQCT was used to measeasure the bone microarchitecture. Results (1) Clinical Spectrum:Adult patients were characterized by short stature (height: 141.4±41.4cm, Z score:-2.78±1.53, presentated with skeletal pains (the common location:knee(72.3%), back(6.6%), hip(29.8%), fatigue (74.5%), fracture (25.5%) and dental problems(76.1%). (2) Biochemical spectrum:Biochemical features contain obvious hypophosphatemia (0.65±0.13 mmol/L), elevated ALP and PTH concentration ALP:137.56±65.05U/L, PTH:93.34±51.71pg/ml) and mild hypocalcemia (2.28±0.95mmol/L). The bone turnover markers P1NP (84.36±58.65 ng/ml), osteocalcin (0.424±0.276 ng/ml) and β-CTX (20.34±12.28 ng/ml) were elevated.(3) Radiological spectrum:The radiological spectrum illustrated wide spread distribution signs of osteomalacia (92.5%). Containing deformation of pelvis (57.5%), thoracolumbar vertebra deformation (35%), pseudo-fracture (15%). BMD of femor neck decreased (Zscore:-0.38±1.36), BMD of lumbar vertebra increased (Zscore: 1.80±1.78). Bone microarchitecture showed decrased Cortical bone Area (Ct.Ar) and vBMD, elevated trabecular area (Tt.Ar). (p<0.001)(4) Musculoskeletal complications:early onset and prevalent osteoarthritis in hip, knee and thoracolumbar were observed (knee OA (7.5%), hip OA (27.5%)), and increase with age. Enthesopathy(55%) and diminished hearing(17%) were also occurred.ConclusionAdult patients with XLH were characterized by① short stature, presentated with skeletal pains, and dental problems. ②Biochemical abnormality and elevated bone turnover markers indicated that the disease was still active. ③The radiological spectrum illustrated wide spread distribution signs of osteomalacia. ④ Bone microarchitecture showed decrased vBMD and Cortical bone Area (Ct.Ar), elevated trabecular area (Tt.Ar).⑤Moreover, early onset and prevalent osteoarthritis in hip and knee were observed, which increase with age. Enthesopathy and diminished hearing were also occurred. These data may improve our understanding of this disease in their adult stage.BackgroundTumor-induced osteomalacia (TIO) is rare acquired hypophosphatemic osteomalacia, and the most common hypophosphatemic osteomalacia that onset in adult stage. The mechanism of the disease is induced by excessive production of fibroblast growth factor 23(FGF23), which causes renal tubular reabsorption of phosphate and hypophosphatemia, resulting in impaired skeletal mineralization. TIO tumors are almost all benign mesenchymal tumors, occurred in a variety of soft tissue and bone sites. Microscopically, Phosphaturic mesenchymal rumors (PMT) share similar histopathologic features:plenty of bland spindled cells, rich in blood vessels, osteoclast-like giant cells, ectopic bone/cartilage like structures or calcification. However, it still remains unclear why excess FGF23 is secreted by PMT tumors and the mechanism of tumor propagate is not clear yet. The studies focus on the tumor genomics remains rare, at present. The recent studies have suggested that fibronectin 1-Fibroblast Growth Factor Receptor 1(FNe1-FGFR1) fusion gene is present in 60% of PMT cases. The presence of the FN1-FGFR1 fusion gene, as the FN1 promoter enhances FGFR1 expression. However, the FN1-FGFR1 fusion gene was presented in soft tissue or bone, the histologic origin was still unknown. Based on the previous studies, we want to identified the presence of the FN1-FGFR1 fusion gene in PMT and explore the clinical and pathological characteristic of tumors presented with fusion gene.Objective1. To explore whether the FN1-FGFR1 fusion gene presented in PMT.2. To analysis the percentage of FN1-FGFR1 fusion of PMT.3. To explore whether the clinical and pathological characteristic of tumors with fusion gene were different from the other.Subjects and Methods1. Subjects:We recruited 45 cases of TIO in Peking Union Medical College Hospital from 2000-2013, they were disgnosed as tumor-induced osteomalacia. The pathological examination revealed phosphaturic mesenchymal tumors, and the serum phosphorus was increased after operation. We collected 20 tumors from other mesenchymal tumors. These tumors were lipomyoma, hemangioma and neurofibroma.2. Methods(1) Fluorescence in situ hybridisation (FISH) was used to detect FN1-FGFR1 fusion gene, and the fluorescent microscope was used to observe the stained sections and take pictures.(2) Observe the HE staining of the experiment and control groups to identify the histological structures and compare the differences of TIO tumors with fusion gene from the others.(3) Collected the clinical data of all the patients, in order to identify the clinical features and compare the differences of patients with fusion gene from the others.Results1. This study enrolled in 45 patients of TIO,12 patients fail in FISH detection. Among the other 33 cases, fluorescence in situ hybridisation analysis showed 9 cases with FN1-FGFR1 fusion gene, positive rate 27.3%.24 cases showed negative of FN1-FGFR1 fusion. The other 20 cases served as control,4 fail in detection, and other 16 cases showed negative results.2. The FNl-FGFR1 fusion gene detected in this study showed gene amplification.3. Among the tumors with FN1-FGFRl fusion gene,7 cases comes from soft tissue,2 roots in paranasal sinus; The FN1-FGFR1 fusion gene negative tumors,10 cases root in soft tissue,8 cases in bones,4 cases in paranasal sinus, the other comes from vertebra.4. There are no statistical differences of clinical feature and biochemical results between the patients with fusion gene and the others. The positive rate of octreotide in tumor with FNl-FGFR1 fusion gene was 44.4%, lower than negative fusion gene (70.8%).5. Tumors with FN1-FGFR1 fusion gene are a single histopathologic entity:short shuttle-like cells, aggregated distribution, rich in osteoclast-like giant cells, severe calcification, also rich in blood vessels (vascular sinus). The manifestations of the tumor negative in fusion gene are varied. A portion of tumor showed abnormal vessel (Staghorn vessel) and fat cells.Conclusion:We observed ① the existence of FN1-FGFR1 fusion gene in the TIO tumors by Fluorescence in situ hybridisation (FISH) method in TIO tumors, the positive rate was 27.3%. ②The fusion gene was amplificatied. ③The positive rate of octreotide in tumor with FN1-FGFR1 fusion gene was 44.4%, lower than negative fusion gene (70.8%). ④Tumors with fusion gene are a single histopathologic entity:aggregated short shuttle-like cells, rich in osteoclast-like giant cells, severe calcification.