Renal osteodystrophy
Summary
Bone disease of chronic kidney disease driven by hyperphosphatemia, decreased calcitriol, hypocalcemia, and secondary hyperparathyroidism. Causes osteitis fibrosa cystica, osteomalacia, and adynamic bone disease.
Detail
In CKD, failing kidneys cannot excrete phosphate or 1-alpha-hydroxylate vitamin D, producing hyperphosphatemia, low calcitriol, and hypocalcemia, which drives compensatory PTH secretion (secondary hyperparathyroidism) and elevated FGF23. Chronic PTH elevation causes high-turnover bone disease (osteitis fibrosa cystica) with subperiosteal resorption and 'brown tumors'; low vitamin D causes osteomalacia (defective mineralization); over-suppression of PTH causes adynamic bone disease. Patients develop bone pain, fractures, and vascular/soft-tissue calcification (calciphylaxis). Treatment: phosphate binders (sevelamer, lanthanum, calcium acetate), calcitriol or cinacalcet, dietary phosphate restriction. Boards: 'hyperphosphatemia + hypocalcemia + high PTH' = CKD-MBD.
Sources
- First Aid for USMLE Step 1 2024
- Pathoma
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