1,25-Vitamin D-mediated hypercalcaemia in the setting of immune therapy-related sarcoid-like reaction.

Summary: We presented a case of a 72-year-old male with severe hypercalcaemia of 3.84 mmol/L following the second cycle of immunotherapy with ipilimumab and nivolumab in the setting of metastatic melanoma with known bone metastases. Further investigations demonstrated hilar lymphadenopathy, which was not present in previous imaging, and subsequent hypercalcaemia work-up demonstrated a significantly elevated serum calcitriol level as high as 429 pmol/L. A diagnosis of drug-induced sarcoid-like reactions or DISRs was made on the basis of hypercalcaemia and hilar lymphadenopathy following immunotherapy. Hypercalcaemia was effectively treated with intravenous fluids and medical therapy including a short course of subcutaneous calcitonin, a total of 120 mg of denosumab and oral prednisolone.

Learning points: DISRs are a rare complication of immunotherapy and may mimic metastases. A temporal relationship between commencement of therapy and progression on clinical imaging is important in making an accurate diagnosis.Calcitriol-mediated hypercalcaemia secondary to DISRs is an important differential diagnosis to hypercalcaemia of malignancy and should be considered in patients who have undergone immunotherapy.Prednisolone should be considered as the next line of treatment after fluid therapy in patients with calcitriol-mediated hypercalcaemia. Prednisolone and denosumab both reach maximum clinical efficacy between 7 and 10 days. Therefore, treatment administration should be spaced out by at least five days to avoid iatrogenic hypocalcaemia.