A 65-Year-Old Man with Parathyroid Independent Hypercalcemia Due to Renal Cell Carcinoma and Resolution of Hypercalcemia Following Nephrectomy; Proposed Mechanisms of Hypercalcemia With Renal Cell Carcinoma

Abstract

We report a case of a 65-year-old man who presented to the Endocrine service for hypercalcemia. He had painful joints, muscle aches, joint stiffness, and incidentally discovered elevated calcium levels on two separate occasions. A lab evaluation indicated non-parathyroid mediated hypercalcemia with calcium levels in the range of 10.1-10.5mg/dl. Parathyroid hormone related peptide (PTHrP) level was undetectable. His PTH and 25-OH Vitamin D levels were normal. But his 1, 25 Dihydroxy Vitamin D levels were low. Initial imaging revealed a heterogeneously enhancing mass on the posterolateral left kidney. Our patient underwent a left nephrectomy, and the mass was identified as RCC on surgical pathology. We illustrated the differential diagnosis of hypercalcemia and the evaluation of hypercalcemia occurring with RCC. This case explains that we need to carefully evaluate, interpret, and review all the data, especially when the patient has borderline elevated calcium levels and does not have a typical presentation of malignancy.