Hyperparathyroidism-induced brown tumor presenting with metastatic bone disease-like skeletal lesions: A case report and literature review

Abstract

A common clinical sign of paraneoplastic syndromes, hypercalcemia can be difficult to diagnose, especially when the primary tumour is unknown. Brown tumour is a benign osteolytic lesion resulting from hyperparathyroidism. Despite being uncommon—its estimated incidence in patients with primary hyperparathyroidism ranges from 1.5% to 4.5%—it can manifest as severe hypercalcemia and skeletal destruction that closely resembles bone metastases. We describe a 37-year-old woman who had a pathological femur fracture and was admitted with severe pain. Significant hypercalcemia and elevated serum creatinine were found during laboratory tests. Considering the patient’s young age, metastatic bone disease was initially suspected as a more probable etiology than multiple myeloma. But we were unable to locate the main tumour. During the acute phase, the management of hypercalcemia and pain control were given top priority. A brown tumour was discovered by histopathological analysis after orthopaedic intervention and bone biopsy at the fracture site. The diagnosis of primary hyperparathyroidism as the underlying aetiology was confirmed by a subsequent endocrinological workup, which revealed noticeably elevated parathyroid hormone (PTH) levels. This case emphasises how crucial it is to keep a wide differential diagnosis in mind when dealing with osteolytic lesions and hypercalcemia, particularly when there is no primary cancer to confirm the diagnosis. Even though brown tumours are uncommon, they should be taken into account in these situations to prevent misdiagnosis and ensure appropriate management. From a clinical and radiographic perspective, brown tumours can closely resemble metastatic bone disease. To achieve diagnostic clarity, a multidisciplinary approach that includes endocrine evaluation and histopathology is essential. Delays in receiving effective treatment can be avoided by identifying primary hyperparathyroidism early.