The latter is most often associated with malignancies and is typically characterized by an acute onset (serum calcium often >3.5 mmol/L), suppressed or low-normal PTH levels, and a high risk of developing hypercalcemic crisis [8,9]. Humoral hypercalcemia mediated by PTHrP accounts for approximately 80% of cases and is the most common cause of malignancy-related hypercalcemia. Clinically, hypercalcemia may manifest as neuropsychiatric symptoms, gastrointestinal disturbances, and renal dysfunction [10,11]. The gene discussed is PTHLH; the disease is Hypercalcemia.