Pembrolizumab-Induced Obstructive Bronchiolitis in a Patient With Stage IV Non-Small-Cell Lung Cancer

Objective: Immune checkpoint inhibitors are now a standard of care for the management of many metastatic cancers, including non-small-cell lung cancer. Pembrolizumab, a selective anti–PD-1 monoclonal antibody, augments the host antitumoural response. This hyperactivation of the immune system has side effects, the so-called immune-related adverse effects. The objective of this case report was to review and point out a new pattern of immune checkpoint inhibitor–associated pneumonitis. Case Description: A 69-year-old woman with stage iv non-small-cell lung cancer receiving pembrolizumab presented for increased dyspnea. Pembrolizumab-related obstructive bronchiolitis was diagnosed based on a new severe obstructive disorder, without bronchodilator reversibility, and mosaic attenuation on angiography, without other identifiable causes. Summary: To our knowledge, this is the first description of a case of pembrolizumab-induced obstructive bronchiolitis. Various patterns of immune checkpoint inhibitor–associated lung disease have been described, and bronchiolitis should be included in the differential diagnosis.