Hemophagocytic Lymphohistiocytosis in a Patient with Rheumatoid Arthritis on Pembrolizumab for Lung Adenocarcinoma.

Immune checkpoint inhibitors have changed the landscape of classic cancer treatment. However, their use is associated with the emergence of new adverse events. An elderly man with rheumatoid arthritis was started on pembrolizumab for newly diagnosed advanced lung cancer. He subsequently developed hemophagocytic lymphohistiocytosis (HLH), which is potentially fatal but has not been properly established as an immune checkpoint inhibition-induced event. We herein report the case of a patient with pembrolizumab-induced HLH.