Pneumonitis incidence might increase if anti‐PD‐1 mAb was combined with other agents, such as anti‐CTLA‐4 mAb,9 also known to carry a risk of pneumonitis.2 In this study, we confirmed these observations and further clarified that anti‐PD‐1 treatment combined with chemotherapy, targeted therapy or CTLA‐4 blockade was also associated with pneumonitis risk, indicating the additive effects of multiple agents on lung‐toxic effects. This evidence concerns the gene CTLA4 and pneumonitis.