Maxillary Brown Tumor Revealing Primary Hyperparathyroidism: A Diagnostic Pitfall Not to Be Missed: A Case Report

Primary hyperparathyroidism is a common endocrinopathy characterized by the autonomous production of parathyroid hormone (PTH), leading to hypercalcemia and hypophosphatemia. Although often diagnosed at an asymptomatic stage, its clinical manifestations can include rare but classic bone and renal complications, such as brown tumors. We report the case of a 73-year-old female patient who presented with an osteolytic swelling of the maxilla. Initial imaging and biopsy suggested a benign giant cell tumor. However, a complete phosphocalcemic panel revealed severe hypercalcemia (2.90 mmol/L), hypophosphatemia (0.65 mmol/L), and a markedly elevated intact PTH (500 pg/mL), confirming the diagnosis of primary hyperparathyroidism. Cervical computed tomography localized a right parathyroid adenoma. The patient successfully underwent targeted parathyroidectomy, which normalized biochemical parameters and led to the regression of the bone lesion. This case illustrates an atypical presentation where a maxillary brown tumor was the initial revealing sign, and underscores the crucial importance of a multidisciplinary diagnostic approach. Any giant cell tumor, particularly in the maxilla, should prompt a thorough endocrinological workup, including measurement of calcium, phosphate, and PTH. Ignoring this association could delay the diagnosis and expose the patient to serious complications. Optimal management requires close collaboration between endocrinologists, maxillofacial surgeons, radiologists, and pathologists to treat both the local tumor and the underlying metabolic disorder.