Metastatic calcinosis cutis due to refractory hypercalcaemia responsive to denosumab in a patient with multiple sclerosis

Metastatic calcinosis cutis results from abnormal calcium levels leading to the precipitation of insoluble calcium salts in the skin and subcutaneous tissue. Here, we present the case of a 67-year-old man with multiple sclerosis on chronic dexamethasone and concurrent supplementation of calcium and daily cholecalciferol presenting with painful calcified lesions. During initial presentation, corrected calcium was 13.8mg/dL (reference range: 8.5-10.1mg/dL), ionised calcium was 1.70mg/dL (reference range: 1.13-1.32mg/dL) and 25-hydroxyvitamin D was 41.6ng/mL (reference range 30-100ng/mL). Normocalcaemia was restored with the off-label use of denosumab, usually reserved for hypercalcaemia of malignancy and intractable osteoporosis. We discuss potential aetiologies of this patient's hypercalcaemia, calcinosis cutis diagnosis and management and the off-label use of denosumab.