MON-501 A Hemangioma Causing Tumor Induced Osteomalacia

Introduction: TIO (Tumor induced osteomalcia) is a rare paraneoplastic syndrome due to ectopic production of FGF23 (Fibroblast growth factor 23) from a mesenchymal tumor that results in renal phosphate wasting and impaired calcitriol synthesis. We present a case of TIO from a benign hemangioma which is an uncommon occurrence. Clinical case: A 68-year-old female presented with a history of multiple fractures; right pelvic fracture 8 years ago, bilateral pubic rami fractures 3 months ago, left femoral neck fracture and left humeral shaft fracture 1 month ago due to trivial traumas. She also complained of chronic generalized muscle pain and severe fatigue that essentially made her bedbound. Her past medical history was significant for DM type II, hypertension, hyperlipidemia, osteoarthritis and chronic anemia. She was diagnosed with a right inferior parathyroid adenoma after noting high PTH of 281pg/ml [15-65] and increased uptake on a parathyroid scan. Following a right inferior parathyroidectomy, the PTH was 51pg/ml [15-65]. Current workup: Vitamin D 7.4pg/ml [30-80], Calcium 7.0mg/dl [8.6-10.2] (corrected calcium 8.0mg/dl), Phosphorous 1.4mg/dl [2.7-4.5], Magnesium 1.6mg/dl [1.7-2.6], Alkaline phosphatase 222U/l [35-104] , Creatinine 0.6mg/dl [0.5-1.2], PTH 214.4pg/ml [15-65] and normal transaminases. Whole body bone scan showed increased uptake in multiple foci in the bilateral ribs, sternum, both shoulders and left humerus. About 2 weeks following vitamin D and calcium supplementation, serum calcium normalized, vitamin D improved to 15pg/ml [30-80] and PTH trended down to normal limits at 52.4pg/ml [15-65]. But the phosphorous level was never >1.6mg/dl [2.7-4.5] despite vigorous IV and oral replacement. This raised concern for hypophosphatemic osteomalacia. Incidentally, as workup for back pain and acute on chronic anemia, a CT abdomen was done which showed a heterogeneously enhancing right pelvic mass measuring up to 7.5 cm extending into the spinal canal from approximately L4-5 level into the upper sacrum. MRI confirmed the presacral mass. A CT guided biopsy was done and final pathology reported hemangioma by STAT6 immunostain. 1,25 (OH)2 Vitamin D was 24 pg/ml [18-78] and an FGF23 level was very high at 3980 RU/mL [<=180] confirming our diagnosis of TIO. Although surgery would have been curative in TIO, this patient was tired of surgeries and decided to go with medical management. Calcitriol 0.25mcg bid, K-Phos Neutral 1 tablet four times a day at equal intervals throughout the awake hours was recommended. Conclusion: TIO is a rare disorder that is usually caused by benign mesenchymal tumors. Although rare, hemangiomas can cause TIO.