The patient was admitted to the hospital for treatment of hypercalcemia and hypokalemia and for work-up of elevated alkaline phosphatase and abdominal pain. Upon admission, serum ionized calcium measurement confirmed true hypercalcemia. Additional diagnostic tests were then ordered to help differentiate between parathyroid hormone (PTH)–mediated and non-PTH–mediated causes for the hypercalcemia (see Table 2).
The patient’s PTH level was normal and the urine fractional excretion of calcium level was high, ruling out familial hypocalciuric hypercalcemia (FHH), in which urine calcium level is low. A measurement of PTH-related protein (PTHrP), secreted by some cancers, was normal, suggesting exclusion of solid tumor malignancy. Vitamin D toxicity was ruled out because the patient’s 1,25-dihydroxyvitamin D level was low.
The patient continued to experience vague abdominal, back, and rib pain that seemed to migrate daily and worsened with movement. A skeletal x-ray was performed and revealed numerous lytic lesions of the skull (Figure 1), midright humerus (Figure 2), and distal left radius.
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