MON-349 Left Hip Pseudofracture in a Patient with Refractory Paget Disease of the Bone

Background Paget’s disease of the Bone (PDB) is a benign condition caused by focal abnormal bone remodeling. It is largely asymptomatic and is often discovered incidentally while investigating an elevated alkaline phosphatase (ALP) or imaging studies. Diagnosis relies on biochemical screening, ALP, as a first line test. X-rays and radionuclide scans can assist in determining the extent of disease. Bisphosphonates are recommended for the treatment of bone pain associated with PDB. Zoledronic acid is recommended as the bisphosphonate most likely to give a favorable pain response. Treatment aimed at improving symptoms is recommended over a treat-to-target strategy aimed at normalizing total ALP in PDB. Clinical case A 51-year-old, non-verbal female presented to the Endocrinology office with her legal guardian for a follow-up regarding Paget’s disease of the bone. The patient had a past medical history of mental disability and refractory Paget’s disease that was diagnosed 13 years prior in the setting of elevated alkaline phosphatase. At the time of diagnosis bone scan showed involvement of both tibias, pelvis and right femur stress fracture. She also had a right femoral fracture 7 years before the current presentation that was surgically fixed with an intramedullary rod. The patient had undergone 5 yearly infusions of Zoledronic acid with persistent elevated alkaline phosphatase. During her clinic visit the patient endorsed left non-traumatic hip pain as well as difficulty walking over the last 2 weeks. Vital signs were within normal limits. On physical exam she appeared well developed, no acute distress was noted, normal heart rate, regular rhythm and normal heart sounds. Pulmonary effort was normal, no respiratory distress or abnormal sounds were appreciated. Musculoskeletal exhibited bilateral lower extremity bowing. No skin warmth, bony growths or tenderness on palpation were noted. Lab work revealed ALP 277 u/l, bone specific alkaline phosphatase 95.9 (8.1 - 31.6), BUN 12 mg/dl, Creatinine 0.66 mg/dl, GFR 90, Calcium 9.0 mg/dl, Vitamin D 23.3 ng/mL. She had been treating the hip pain with as needed NSAIDs. An X-ray of the left femur was ordered, and the study showed possible acute subcapital minimally displaced femoral neck fracture with minimal impaction in the setting of known Paget’s disease. The patient was then contacted and asked to present to the ER emergently for further evaluation and treatment. Upon arrival to the Emergency Department, an MRI of the left hip was performed, demonstrating extensive Paget’s disease with no evidence of acute hip fracture. Conclusions It is essential to obtain an urgent x-ray in patients with Paget’s disease who presents with localized pain. However as this case demonstrates x-ray findings can be misleading due to underlying structural deformity of the bone and further imaging like CT or MRI may be necessary.