SAT240 Recurrent Hypercalcemia Due To 1,25 Dihydroxy Vitamin D Elevation Of Unclear Etiology

Abstract Disclosure: A. Javvaji: None. C. Anastasopoulou: None. Introduction: Recurrent Hypercalcemia is common with primary hyperparathyroidism and malignancy accounting for 90% of cases. Extra renal activation of 1α-hydroxylase with subsequent elevation of 1,25 dihydroxy vitamin D is a relatively uncommon cause of hypercalcemia. Herein, we report an unusual case of recurrent hypercalcemia due to elevated 1,25 dihydroxy vitamin D of unclear etiology, resistant to therapy with denosumab or bisphosphonate that responded to glucocorticoid therapy. Case Presentation: A 68 year old female was admitted to the hospital for worsening calcium with symptoms of polyuria and increased thirst. Review of systems and physical examination were otherwise unremarkable. Initial work-up demonstrated calcium level of 11.7mg/dL (8.7-10.3), creatinine 2.58 mg/dL (0.57-1), PTH 8pg/mL (15-65), Kappa/Lamba ratio 1.82 (0.26-1.6), PTHrP 11pg/mL (11-20), 25 (OH) Vitamin D 14ng/mL (30-100), 24,25 Dihydroxy Vitamin D ratio 25.81 (<25). Bone marrow biopsy, kidney biopsy, and myeloma work up were all unremarkable. Imaging studies including whole body CT and PET CT were also unremarkable. In the acute phase patient was treated with zoledronic acid and later denosumab with only temporary decrease in calcium levels. Ultimately, she responded well to prednisone therapy. Further work-up for finding the underlying cause of elevated 1,25 dihydroxy vitamin D remains ongoing. Discussion: Elevated 1,25 dihydroxy vitamin D level in granulomatous, neoplastic, and certain unusual diseases is well recognized as a cause of hypercalcemia. These levels may be exacerbated by increased intake of calcitriol, or by extra-renal production in granulomatous and lymphoproliferative diseases. Other rare causes of elevated 1,25 dihydroxy vitamin D include granulomatosis with polyangiitis, cat scratch fever, talc granulomatosis, Crohn’s disease, silicone granulomatosis. Patients with all these diseases respond well to steroids and that was another sign that further work-up to find the source of the elevated 1,25 dihydroxy vitamin D in our case is essential. Conclusion: In patients with recurrent hypercalcemia and elevated 1,25 dihydroxy vitamin D levels, a complete work-up for underlying malignancy, granulomatous or other unusual diseases is indicated. Glucocorticoid therapy is the most effective way to control the hypercalcemia related to increased 1,25 dihydroxy vitamin D even in the long-term phase, especially until the main cause of the problem is identified and treated appropriately. Presentation: Saturday, June 17, 2023