Double-phase scintigraphy using Tc-99m sestamibi MIBI is the study of choice for detecting parathyroid adenoma in patients with primary hyperparathyroidism. However, before parathyroid imaging, these patients may uncommonly present with multiple osteolytic lesions and bone scan findings consistent with metastatic disease. By excluding malignancy, the diagnosis of osteitis fibrosa cystica and parathyroid adenoma may subsequently be confirmed. The authors describe the case of an elderly patient who presented with imaging findings initially masquerading as metastatic disease. When parathyroid adenoma was finally diagnosed with Tc-99m MIBI imaging, radiopharmaceutical uptake was also noted within several brown tumors, including clinically significant brown tumors of the left lower extremity, a finding that has not been previously reported.