Immune Checkpoint Inhibitor-Induced Primary Hyperparathyroidism in a Small-Cell Lung Cancer Patient: A Case Report.

Immunotherapy is increasingly being used in the treatment of tumors. Adverse effects, however, are not uncommon, with the most common immune-related adverse events (IrAEs) including rash, fatigue, anemia, diarrhea, constipation, and elevated transaminase, among others. Rare IrAEs, which may include thrombocytopenia, hypoparathyroidism, pancreatitis glomerulonephritis, Guillain-Barré syndrome, and celiac disease, may also present. Immune checkpoint inhibitor (ICI)-induced primary hyperparathyroidism (PHPT) has not yet been reported on, and no research currently exists regarding its pathogenesis. We describe how a 50-year-old man diagnosed with advanced small-cell lung cancer (SCLC) developed severe PHPT after receiving the programmed cell death (PD)-1 inhibitor camrelizumab. The patient eventually died of respiratory failure and a progressive malignancy. We speculate that the hypercalcemia and hypophosphatemia observed in this case were secondary to ICI-induced PHPT. Although fatal PHPT is rare, early intervention may reduce the risk of future complications. Therefore, further exploration of the underlying mechanisms is needed to guide solutions.