MON-777 Therapeutic Challenges In Post-Transplant Renal Osteodystrophy

Abstract Disclosure: R. Hilder: None. E. Berg: None. J. Weinreb: None. Background: Renal osteodystrophy is defined as abnormal bone histology and noted to be one component of metabolic bone disease associated with chronic kidney disease (CKD-MBD). It can be challenging to manage, and this challenge may be even greater post renal transplant due to the development of tertiary hyperparathyroidism (HPT). Here we report a case of severe tertiary HPT with osteitis fibrosa cystica and vitamin D deficiency. Clinical Case: A 29-year-old man with ESRD now 8 months post deceased donor renal transplant was evaluated for right hip pain. Labs showed calcium 8.4 mg/dL (reference range 8.6-10.4 mg/dL), phosphorus 3.1 mg/dL (2.3-4.4 mg/dL), albumin 4.4 mg/dL (3.9-5.0 mg/dL), Parathyroid hormone (PTH) 1223 pg/mL (11-51 pg/mL) creatinine 1.46 mg/dL from baseline 1.1mg/dL (0.6-1.3 mg/dL), ALP 952 U/L (37-113 U/L) and 25-hydroxy vitamin D 9 ng/mL (20-50 ng/mL). MRI revealed a multiloculated lesion in the right iliac bone and pubic ramus fracture. Biopsy showed lamellar and woven bone, fibrous tissue, and hemosiderin consistent with a brown tumor. Thyroid ultrasound revealed a 17 mm hypoechoic nodule consistent with a parathyroid adenoma. He was diagnosed with tertiary HPT, right iliac osteitis fibrosa cystica, and vitamin D deficiency-related osteomalacia.Notably, immediately following transplantation, PTH was >1700 pg/mL, prompting initiation of cinacalcet. Despite titration of cinacalcet, PTH remained markedly elevated and ergocalciferol 1250 mcg weekly was initiated, with resultant high normal serum calcium. Definitive treatment required referral for parathyroidectomy given severe tertiary HPT and osteitis fibrosa cystica. Conclusion: This case highlights an uncommon bone pathology, osteitis fibrosa cystica, as well as therapeutic challenges in the management of CKD-MBD with persistently elevated PTH. Although cinacalcet may lower PTH and improve calcium-phosphorus balance, nodular parathyroid glands do not involute. This is in part due to the downregulation of calcium sensing receptors and vitamin D receptors on these cells, and the high PTH with hypercalcemia often persists post-transplant. Persistent PTH elevation 6 months after transplantation is consistent with tertiary HPT. Hypovitaminosis D likely masked hypercalcemia in this case; thus, ergocalciferol was initiated cautiously, and calcium was monitored as it rose to the high normal range. Surgical intervention is usually deferred for 6-12 months post-transplantation while hormonal and electrolyte levels re-equilibrate, but parathyroidectomy remains the recommended treatment for persistent tertiary HPT refractory to medical therapy. This has been associated with marked improvement in bone mineral density and improvement in progression of brown tumors. Presentation: Monday, July 14, 2025