Vertebral Fractures as a Manifestation of Phosphaturic Mesenchymal Tumor-Induced Osteomalacia

Background. The rarity of the disease and, in this regard, the lack of doctors awareness about the pathology, late diagnosis and severe complications of the musculoskeletal system emphasize the relevance of clinical case demonstrating. The uniqueness of the case lies in the fact that hypophosphatemia, noted 3 years after the disease debut, was not taken into account.Case description. A 45-year-old patient with complaints of muscle weakness, gait disorders, torso deformity and multiple vertebral body fractures that appeared against the background of any somatic diseases absence, a differential diagnosis of metastatic vertebral bodies lesions and secondary osteoporosis complicated by vertebral body fractures was carried out for four years in various hospitals, and was even treated with bisphosphonates. Against this background, the chest deformity increased, kyphosis and remodeling fractures of other bones appeared. The assessment of calcium and phosphorus homeostasis was first performed at the 4th year of the disease, but the detected hypophosphatemia was not regarded as a manifestation of hypophosphatemic osteomalacia.Conclusion. Among adult patients with multiple low-energy fractures, severe muscle weakness and bone pain that appeared against the background of complete health, to exclude hypophosphatemic osteomalacia induced by mesenchymal tumor, it is necessary to include the level of phosphorus in blood and daily urine assessment in the diagnostic algorithm.

Fanconi Syndrome Leading to Hypophosphatemic Osteomalacia Related to Tenofovir Use

Tenofovir disoproxil fumarate (TDF) is used worldwide to treat and prevent Human Immunodeficiency Virus (HIV) infection. Fanconi syndrome is a complication of TDF use and is characterized by inadequate reabsorption of glucose, phosphate and protein in the proximal tubule of the kidney which may eventually lead to osteomalacia manifested by symptoms of pain, muscular weakness and difficulty ambulating. We present a patient with severe osteomalacia due to progressive and unrecognized Fanconi’s syndrome, who responded rapidly to TDF withdrawal, oral phosphate repletion and calcitriol. With the widespread use of TDF-containing antiviral regimens, it is critically important that physicians adhere to screening recommendations to detect early Fanconi syndrome, and recognize symptoms of osteomalacia as a serious complication.

Glomus Tumor: An Unusual Cause of Hypophosphatemic Osteomalacia

Background: Tumor-induced osteomalacia (TIO) is a rare condition resulting in hypophosphatemic osteomalacia. We present a rare case of TIO secondary to glomus tumor. Clinical Case: A 39-year-old woman with history of chronic sinusitis presented with progressively worsening generalized body pain and muscle weakness of eight months duration. Examination showed decreased muscle strength in bilateral upper and lower extremities and congenital cleft palate. Laboratory work up revealed elevated alkaline phosphatase 603 U/L (44–147 U/L), low serum phosphorus 1.5 mg/dL (3.5–5.0 mg/dL), normal serum calcium 8.9 mg/dL (8.3–10.4 mg/dL), normal 25-hydroxyvitamin D 32 ng/dL (30–100 ng/dL), elevated 1,25-dihydroxyvitamin D 62 g/mL (20–45 pg/mL), elevated intact PTH level 99.01 pg/mL (8–74 pg/mL), high normal 24 hour urinary phosphate levels 1100 mg/dl, and elevated FGF23 level 128 RU/mL (<108 RU/mL). Fractional excretion of filtered phosphate (FEPO4) [FEPO4 = (Urine phosphate / Serum phosphate) / (Urine creatinine / Serum creatinine) * 100] was 107.54 % (normal range <20%). Tubular reabsorption of phosphate (TRP) [Percentage TRP = 100 * {1- (Urine phosphate / Serum phosphate) / (Urine creatinine / Serum creatinine)}] was -7.54 %. Tubular maximum reabsorption of phosphate to glomerular filtration rate (TmP/GFR) calculated using formula [TmP/GFR = TRP x serum phosphate] was -0.1131 mg /dL (2.8–4.2 mg/dL). Bone densitometry revealed normal bone density and parathyroid scintigraphy was negative for adenoma. Clinical symptoms along with biochemical evidence of phosphate wasting confirmed by low TRP and an unsuppressed FGF23 levels suggested oncogenic osteomalacia as underlying etiology. Whole body bone scan demonstrated increased radiotracer uptake in the elbows, spine, sacroiliac joints, knees, ankles and multiple ribs suggestive of inflammatory process. MRI of paranasal sinuses revealed large soft tissue mass occupying right frontal, ethmoid, maxillary and sphenoid sinuses suggestive of sinonasal polyposis. 99mTc-Octreotide scan confirmed increased uptake in the nasopharynx. The sinonasal mass was resected and pathology revealed the mass to be a glomus tumor confirmed on immune histochemical studies with positive staining for vimentin and SMA and Ki67 of 5–10 %. Postoperatively, phosphorus levels normalized to 3 mg/dl on day 7. Conclusion: Glomus tumor as cause of TIO is extremely rare however localization and surgical resection of tumor can result in complete resolution of biochemical and clinical manifestations. References: 1. Minisola, S., et al., Tumour-induced osteomalacia. Nat Rev Dis Primers, 2017. 3: p. 17044.

Utility of 18F-AlF-NOTA-octreotide PET/CT in the localization of Tumor-Induced Osteomalacia

Purpose Tumor-induced osteomalacia (TIO) is a paraneoplastic disorder, usually caused by benign mesenchymal tumors that produce high levels of the hormone fibroblast-growth-factor 23 (FGF23). The only curative therapy of the disease is resection of the causative tumors. This research was conducted to evaluate the efficacy of 18F-AlF-NOTA-octreotide ( 18F-OC) PET/CT in detecting TIO and its impact on patient management. Methods Retrospective analysis of 17 patients with hypophosphatemic osteomalacia suspected of TIO was performed. 18F-OC PET/CT study was performed in all 17 patients to localize the tumor. 68Ga-DOTATATE PET/CT was performed in 4 out of 17 patients. 18F-OC and 68Ga-DOTATATE PET/CT studies were performed within 1 week of each other. Both studies were interpreted blindly without the knowledge of other imaging findings. The image findings were compared with the results of histopathological examinations and clinical follow-ups. Results 18F-OC PET/CT scans were positive in 14 patients. Moreover, 4 out of 14 patients were performed with both 18F-OC and 68Ga-DOTATATE PET/CT. Both studies were able to localize the tumor in all the 4 patients. In total, 14 patients had surgery to remove the lesions. Postsurgical pathological examination confirmed causative tumors in these patients whose symptoms diminished promptly. The serum phosphate levels became normal confirming the diagnosis of TIO. 18F-OC PET/CT sensitivity, specificity and accuracy were 87.5%, 100% and 88.2% respectively. 18F-OC PET/CT findings affected patient management in 88.2% of cases. Conclusion 18F-OC PET/CT scan is useful in the detection of tumors causing TIO. Further studies with larger patient population are needed to validate the result.