Proptosis in a child with chronic kidney disease: Answers

Abstract

Answer 1: Brown tumor. Brown tumor (osteitis fibrosa cystica) is a benign and reactive lesion as a result of disturbed bone remodeling due to secondary hyperparathyroidism [1]. Brown tumor is a rare complication of secondary hyperparathyroidism in patients undergoing long-term dialysis. Although Brown tumors usually occur in the long bones, ribs, pelvis and mandible, they can be found in different bones and soft tissue [2]. Answer 2: The cause of Brown tumor is renal osteodystrophy due to secondary hyperparathyroidism. Renal osteodystrophy is a specific term used to describe the histological changes in the bone associated with chronic kidney disease (CKD) [3]. The traditional types of renal osteodystrophy are osteitis fibrosa, osteomalacia, adynamic and mixed [4]. Brown tumor develops only in the osteitis fibrosa cystica form, from long-standing increase in parathyroid hormone (PTH) levels [5]. Answer 3: Numerous osteoclast-like multinucleated giant cells in fibrous stroma with many spindle-shaped cells and hemorrhagic areas are seen on pathologic examination of this patient (Fig. 3). These findings were considered to be Brown tumor of the maxilla. The term “brown tumor” is derived from the appearance of brownish color of the lesion, which is caused by abundant vascularized fibrous tissue and hemorrhage, as well as deposits of hemosiderin on biopsy [6]. Answer 4: Treatment of Brown tumor in our patient was based on management of secondary hyperparathyroidism, and surgical excision of the mass causing proptosis. Management of secondary hyperparathyroidism in our patient was based on reducing dietary phosphate intake and administering phosphate binders, vitamin D, intravenous calcitriol and effective dialysis. Parathyroidectomy is recommended when medical/ pharmacological therapy fails [4]. Secondary hyperparathyroidism was controlled with medical therapy and parathyroidectomy was not required in our patient.