Four mechanisms are responsible: Local osteolysis, humoral hypercalcemia driven by parathyroid hormone‐related protein (PTH‐rP), hypercalcemia mediated by 1.25‐dihydroxyvitamin D, and ectopic hyperparathyroidism, though the latter two are rare [3, 4]. Here, BLOC1S3 is linked to Hypercalcemia.