A Case of Pneumocystis jirovecci in a Patient with Non-Small Cell Lung Cancer Treated with Immunotherapy.

Immune checkpoint inhibitors have become the standard of care in the management of metastatic non-small cell lung cancer (NSCLC) and are associated with improved outcomes when compared to traditional chemotherapy regimens. However, they present with their own unique set of immune-related side effects. One immune-related adverse effect that can arise is pneumonitis, where patients present with dyspnea with nonspecific radiologic findings, making it challenging to differentiate from other etiologies causing dyspnea. We present a case of a 58-year-old woman with NSCLC previously treated with immunotherapy, who presented with shortness of breath. She was initially thought to have immune-related pneumonitis and was treated with immunosuppressive therapy. After several days of treatment, bronchoscopy demonstrated a positive polymerase chain reaction (PCR) for Pneumocystis jirovecii (PJP) after an initial negative direct fluorescent antibody (DFA). The patient was started on appropriate management for PJP and no further immunosuppressive therapy was given.