Calciphylaxis in Association With Hungry Bone Syndrome. A Possible Risk Factor?

Background: Calciphylaxis (calcific uremic arteriolopathy) is a rare complication seen in, although not limited to, patients with end-stage renal disease (ESRD). The abnormal regulation of calcium (Ca) and phosphorus (P) homeostasis in this patient group results in intravascular Ca deposition. These patients often develop secondary/tertiary hyperparathyroidism, presenting unique treatment challenges. When patients do not respond to medical therapy, parathyroidectomy is an option that may be complicated by hungry bone syndrome (HBS). We present a case of a patient with calciphylaxis with HBS post-parathyroidectomy. Case Report: The patient is a 41 y.o. male with ESRD on hemodialysis who presented with lower extremity ulcers complicated by calciphylaxis. On admission, the PTH was elevated at 2200 U with a normal corrected Ca 8.7 and P 8.5. He was found to have a non-displaced pathologic fracture of the right femoral neck. CT scan of the neck revealed nodular parathyroid hyperplasia affecting all four glands. His hyperparathyroidism was managed medically with cinacalcet, phosphate binder, and sodium thiosulfate to optimize his condition before surgery. He underwent a subtotal parathyroidectomy, with post-op course complicated by HBS. Repeat labs showed PTH 444, P 6.1, corrected Ca 7.4, and ionized Ca <4. Despite frequent repletion with IV Ca and addition of calcitriol, he remained persistently hypocalcemic with symptoms (paresthesia, perioral numbness) and prolonged QTc (560 ms) on 12-lead EKG. After weighing the more imminent risk of unstable arrhythmia versus exacerbation of HBS by targeting too high of a Ca level post-op, ICU admission was decided where Ca levels could be more closely monitored and titrated. The patient eventually demonstrated an improvement in his Ca level and symptoms. Discussion: This patient with ESRD complicated by hyperparathyroidism presented with ulcers and calciphylaxis refractory to medical therapy, requiring parathyroidectomy. HBS was a concern in this particular patient given his risk factors. Hypocalcemia is an expected electrolyte imbalance that usually resolves within 2–4 days after parathyroidectomy. Severe and persistent hypocalcemia on day 4 after the procedure should raise concern for HBS. It has been shown that the risk is higher in patients who have secondary hyperparathyroidism, prolonged duration of elevated PTH, age >60, and radiologic evidence of bone disease. ConclusionCalciphylaxis is an uncommon but potentially fatal illness seen in ESRD patients associated with Ca and P abnormalities. Whether this may increase the risk of HBS status-post parathyroidectomy is unknown; however, HBS requiring ICU management to treat refractory hypocalcemia has been reported in this group1. It is arguable that calciphylaxis may serve to identify such patients. (1) Hassanein M, et al. BMJ Case Rep 2018;11:e226696. doi:10.1136/bcr-2018–226696