Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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December 2, 2021
Renal Osteodystrophy with Brown Tumors
- Background:
- Renal osteodystrophy (ROD) is histologically classified into high bone turnover (osteitis fibrosa cystica), low bone turnover (osteomalacia and adynamic bone), or mixed disease.
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Secondary hyperparathyroidism is the leading cause of high turnover in ROD. It is a byproduct of hyperphosphatemia, negative calcium balance, parathyroid hormone (PTH) resistance, and increased PTH activity.
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Brown tumors are seen in the setting of advanced primary (eg, parathyroid carcinoma) or secondary hyperparathyroidism. They consist of cystic/hemorrhagic lesions and highly vascularized fibrous tissue.
- Clinical Presentation:
- Patients are usually asymptomatic.
- Pain may occur in the setting of superimposed fracture.
- Key Diagnostic Features:
- ROD in skull: Thickening, sclerosis, granular demineralization with “salt and pepper” appearance, blurring of inner and outer tables
- ROD in spine: Thickening of the primary (vertical) trabeculae, resorption of the secondary (horizontal) trabeculae, endplate erosion, and dense sclerotic bands with hazy borders along the endplates (“rugger jersey” spine)
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Brown tumors: Lytic-appearing on CT/radiography with sharp zone of transition; classically T2 hyperintense and cystic-appearing on MRI but there may be enhancement of fibrovascular tissue and septae
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Parathyroid hormone levels are used to follow disease activity but are inaccurate diagnostic tools.
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Biopsy is the gold standard to determine the subtype of ROD.
- Differential Diagnoses:
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Metastases: Can result in lytic and/or sclerotic lesions; may be indistinguishable from brown tumors, as the latter can also enhance with contrast; metastases will not result in trabecular thickening.
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Osteopetrosis: "Bone within a bone" cortical thickening around the entire vertebral body border; can also have dense bands paralleling the endplates, however, these are well demarcated as opposed to the “rugger jersey” spine
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Paget disease: Thickened and disorganized trabeculae; sclerotic “picture frame” around the vertebra and osseous expansion; localized rather than the diffuse involvement seen in ROD
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Treatment:
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Phosphate-lowering therapy, maintaining serum calcium, calcitriol and vitamin D analogues, and antiresorptive medications
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Treatment is personalized based on multiple factors outlined by the Kidney Disease Improving Global Outcomes (KDIGO) guidelines.
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