PTHLH and hypercalcemia disease: Clinicians should be alert to key red flags (poor steroid response, systemic symptoms, refractory hypercalcemia, unexplained weight loss and persistent fever), obtain a targeted laboratory panel (PTH, phosphate, 25(OH)D, 1,25(OH)2D, PTHrP), and follow an imaging cascade, escalating from PET-CT to endoscopy if indicated by clinical or PET-CT findings suggestive of malignancy.