1-25OH(2)D Mediated Hypercalcemia Secondary to DISR From Immune Checkpoint Inhibitors

Background: Drug induced sarcoid like reactions (DISR) have recently been described as a potential consequence of immune checkpoint inhibitor therapy. However, hypercalcemia associated with DISR has not been reported. Clinical Case: A 72 year old male presented with metastatic melanoma. He initiated therapy with Ipilimumab/Nivolumab (Ipi/Nivo). Three weeks after his first cycle he developed symptomatic hypercalcemia (calcium 14.4 mg/dL), and acute kidney injury (creatinine 3.45mg/dL), PTH 12 pg/mL, 25OHD 51, and PTHrp 0.5. He received IV fluids and IV bisphosphonates and calcium normalized to 9.1 mg/dL and creatinine 1.85 mg/dL. His Ipi/Nivo were stopped due to concern for neurotoxicity. He subsequently switched to Q3week Pembrolizumab (Pembro) and after 2 infusions, he again developed hypercalcemia (calcium 11.8 mg/dL). FDG PET demonstrated a complete radiographic response. Labs showed a 1,25OH(2)D of 103 pg/mL (reference range 19.9–79.3 pg/mL), PTH of 4 pg/mL and calcium of 11.4 mg/dL. He was treated with prednisone 20 mg QD. After 9 days on prednisone, 1,25OH(2)D was 26 pg/mL and calcium 9.4 mg/dL. He took prednisone for 3 weeks total. Repeat labs off prednisone for one week were 1,25OH(2)D of 38 pg/mL and calcium 9.1 mg/dL. He continued on Pembro. After being off steroids for 5 weeks, he developed body aches and swelling of the hands. 1,25OH(2)D increased to 100 pg/mL and calcium to 10 mg/dL. He restarted prednisone and stopped Pembro. Labs one month later showed a 1,25OH(2)D of 45 pg/dL while still on prednisone 10 mg qd and a normal calcium in the mid 9’s. Follow up FDG PET showed hypermetabolic bilateral hilar and mediastinal lymphadenopathy not seen on previous imaging. Ultrasound-guided lymph node biopsy revealed granulomatous lymphadenitis. He was diagnosed with DISR, secondary to immunotherapy with checkpoint inhibitors. He continues on prednisone 10 mg per day and calcium and 1,25OH(2)D levels have remained normal. Conclusion: This is the first case of 1,25OH(2)D mediated hypercalcemia as a consequence of DISR induced by immune checkpoint inhibitor therapy. Hypercalcemia in the setting of malignancy is more commonly due to humoral hypercalcemia of malignancy from PTHrp or bone metastasis, but DISR needs to be a consideration in persons with hypercalcemia on immune checkpoint inhibitor therapy, with elevated 1,25OH(2)D levels and low PTH and PTHrp levels.