Brown Tumor as a Reversible Cause of Osteolytic Lesions in Post-trauma Knee Pain: Role of Timely and Serial Parathyroid Hormone Testing.

Osteitis fibrosa is a metabolic skeletal disorder characterized by increased osteoblast and osteoclast activity, leading to abnormal bone matrix formation secondary to elevated parathyroid hormone (PTH) levels. Brown tumor is a rare and late manifestation of this condition that presents with focal well-defined osteolytic lesions, similar to metastatic disease. We present a case of a 52-year-old male with right knee pain following trauma. X-ray imaging demonstrated lytic lesions and a pathological fracture, ultimately leading to a diagnosis of a brown tumor. This case emphasizes the need to include brown tumors in the differential diagnosis of lytic bone lesions in middle-aged patients and highlights the role of serial PTH testing in identifying this uncommon condition.