Bronchiolitis obliterans after combination immunotherapy with pembrolizumab and ipilimumab

Checkpoint inhibitor therapies are members of a new, groundbreaking class of drugs that reinvigorate the immune system to directly attack tumors. A rare side effect of checkpoint inhibitor therapy is pneumonitis, which typically presents as an interstitial lung disease. In this case report, we present a patient in whom combination therapy with the PD-1 inhibitor pembrolizumab and the CTLA-4 inhibitor ipilimumab induced severe airflow obstruction. This is the first report that shows that checkpoint inhibitors may induce airflow limitation.