Fractional exhaled nitric oxide in checkpoint inhibitor pneumonitis: a case report and literature review.

Checkpoint inhibitor pneumonitis (CIP) is a relatively rare adverse event and a potential cause of death in patients treated with immune checkpoint inhibitors (ICIs). Because the symptoms and signs are nonspecific, the diagnosis of CIP is challenging. Additionally, compared with the biomarkers that can monitor the effect of ICIs, there is less research evaluating markers to monitor CIP. We report a case of CIP induced by camrelizumab in a patient with advanced non-small-cell lung cancer, in which the fractional exhaled nitric oxide levels showed obvious increases. Fractional exhaled nitric oxide may have the potential to monitor the condition of airway inflammation in patients using ICIs.