Objective: To report a case of hypercalcemia associated with parathyroid hormone-related protein (PTHrP) in large cell carcinoma of the lung.
Methods: We present a case of PTHrP-mediated hypercalcemia in a patient with a large cell carcinoma of the lung and review the related literature.
Results: A 43-year-old African American man required medical attention because of lethargy, confusion, and poor oral intake. He had bullous emphysema attributable to a 50-pack-year smoking history. On physical examination, vital signs were normal, he was oriented to place and person but not time, and he had cachexia. Breath sounds were decreased in the left lower lung field. Findings on cardiac and abdominal examination were normal. Results of laboratory studies (and corresponding reference ranges) were as follows: calcium 12.1 mg/dL (8.5 to 10.5), albumin 2.0 g/dL (3.5 to 5.0), phosphorus 2 mg/dL (2.5 to 4.5), alkaline phosphatase 68 U/L (40 to 150), intact parathyroid hormone 5 pg/mL (10 to 60), PTHrP 7.0 pmol/L (0.0 to 1.5), 1,25-dihydroxyvitamin D 20.8 pg/mL (25.1 to 66.1), and 25-hydroxyvitamin D 3.7 ng/mL (10 to 60). Computed tomographic scans of the chest showed a large complex lesion in the left lower hemithorax, a small right pleural effusion, and extensive pulmonary emphysema bilaterally. Open lung biopsy revealed a large cell undifferentiated carcinoma. Abdominal and pelvic computed tomographic scans showed no evidence of metastatic involvement. A bone scan was negative for osseous metastatic lesions.
Conclusion: Although the finding is rare, patients with large cell carcinoma of the lung and hypercalcemia may have humoral hypercalcemia mediated by PTHrP.