Brown Tumor Takes an Elbow: A Rare Twist in Renal Bone Disease

Introduction: Brown tumors are rare, osteolytic bone lesions that occur as a manifestation of excessive bone turnover in hyperparathyroidism resulting from PTH stimulation, leading to increased osteoclastic activity, bone resorption, fibrosis, and hemorrhage. Brown tumors are more commonly observed in patients with severe, prolonged HPT, particularly in secondary HPT due to CKD. The prevalence of brown’s tumors in ESRD is between 1.5-1.7%. Case Description: 32-year-old male with PMHx of ESRD secondary to diabetic nephropathy on HD 3x week. PE revealed a firm, tender mass over the lateral aspect of the elbow, with darkening of the skin. Lab results showed elevated serum PTH, phosphate, and alkaline phosphatase, with low-normal calcium. XR of the elbow revealed bulky soft tissue dorsal to the elbow compatible with chronic kidney failure. Conservative management with intensified phosphate control and Vit D analogs. Persistent HPT and the underlying ESRD led to renal transplantation. Post-transplantation, renal function and PTH levels gradually normalized over 8 months. Discussion: Patient presented with an unusual location of Brown’s tumor in the elbow, highlighting the need for a high index of suspicion in ESRD with lytic bone lesions. Restoration of kidney function led to improved calcium-phosphate homeostasis and regression of the lesion, confirming the diagnosis.