MON-347 Osteitis Fibrosa Cystica and Pathological Fractures: The Classic but Neglected Skeletal Manifestation of Primary Hyperparathyroidism

Abstract

Background: Osteitis fibrosa cystica is one of the classic manifestations of primary hyperparathyroidism (PHPT), yet it has become increasingly rare due to early detection of PHPT. Clinical case: A 37-year-old woman was referred to our hospital for fixation of multiple fractures. Before transferring to our hospital, she was admitted to a local hospital due to right distal humerus and left tibial fractures without history of trauma. During the hospitalization, a new fracture at left femur had occurred. Her past medical history was significant for fractures of right shoulder, left elbow and right femur when she fell on the ground 5 years ago and treated by fixation. She had a history of kidney stones in the remote past. She denied family history of calcium or skeletal disorders.Clinical examination revealed gross deformities at right elbow, left thigh and painful swelling of the left tibia. On HEENT examination, there were no palpable neck masses.Upon review of plain radiographs from outside hospital, we found not only fractures but diffuse osteopenia and brown tumors at multiple sites including shaft of right humerus, right proximal radius, left proximal femoral shaft and left tibia. Skull X-ray showed salt-and-pepper appearance. There were prominent subendplate densities at multiple lumbar spines (Rugger-jersey spine). These findings were consistent with osteitis fibrosa cystica which prompted further laboratory investigation for PHPT. The patient had a high corrected serum calcium level of 13.6 (8.6-10.0) mg/dl, low serum phosphate of 2.2 (2.5-4.5) mg/dL, serum creatinine of 1.16 (0.51-0.95) mg/dL, glomerular filtration rate (GFR) of 60.29 ml/min, high serum alkaline phosphatase of 1,482 (35-105) U/L. The serum parathyroid hormone (PTH) level was significantly high at 3,850 (15-65) pg/mL. Vitamin D level was low at 5.98 (≥30) ng/mL.The patient was diagnosed with PHPT. The left lower parathyroid adenoma was identified by 99mTc-Sestamibi scan with single photon emission computed tomography and neck ultrasound. Given severe skeletal manifestations and extremely elevated PTH level, urgent parathyroidectomy was performed. A 2.5-cm parathyroid adenoma was removed which was histologically confirmed by a pathologist. Postoperatively, she developed a hungry bone syndrome which resolved 10 months after. Clinical lesson: In current practice, skeletal manifestation of PHPT is uncommon with a reported incidence of 1.4% in US. Osteitis fibrosa cystica is a radiographic feature of PHPT characterized by demineralized skeleton, salt-and-pepper appearance of the skull, subperiosteal resorption of the phalanges, bone cysts, and brown tumors. Although PHPT has evolved to asymptomatic disease in majority of patients, the classic skeletal involvement should not be overlooked, particularly in young patients who present with multiple pathological fractures.