Multiple Brown Tumors Caused by Primary Hyperparathyroidism as a Differential Diagnosis to Multiple Osteolytic Bone Metastases: A Case Report

Brown tumors are benign osteolytic lesions, which usually respect the bone cortex. Since these lesions may resemble bone metastases, it is important to consider them as a potential differential diagnosis. They occur as a result of increased parathyroid hormone (PTH) secretion mainly due to primary or secondary hyperparathyroidism. We present a case of multiple osteolytic lesions incidentally found on X-ray examinations in a patient, who had a radius fracture after a low-energy trauma. Due to the suspicion of multiple bone metastases, one of them mimicking sequels after a pathological fracture in the ulna, the patient had a positron emission tomography/computed tomography (PET/CT) and a magnetic resonance imaging (MRI) scan performed supporting the existence of pervasive bone lesions without suggesting a primary malignancy. The blood samples showed highly elevated ionized calcium and PTH levels. Therefore, an ultrasound examination and parathyroid scintigraphy were performed, revealing a hyperfunctioning parathyroid adenoma. After removal of the adenoma, the PTH level normalised and the bone changes regressed without surgical intervention. J Endocrinol Metab. 2020;10(3-4):94-100 doi: https://doi.org/10.14740/jem637