Pulmonary nocardiosis following pembrolizumab use: case report and literature review of nocardiosis associated with immune checkpoint inhibitors.

A woman in her 80s, who had a history of treatment with pembrolizumab for biliary tract cancer and was taking low-dose corticosteroids for immune-related adverse events (irAEs) involving nephritis and hepatitis, was admitted to the hospital complaining of a cough and increased sputum production that had begun two weeks prior. Computed tomography (CT) revealed patchy infiltrates predominantly in the lower lobes of both lungs. Since one of the Nocardia species was detected in the sputum collected at admission, we diagnosed her with pulmonary nocardiosis. In addition to this case, other cases of nocardiosis that developed following the use of immune checkpoint inhibitors (ICIs) have been reported. These cases include instances in which nocardiosis developed despite the absence of immunosuppressive therapy. Here, we review nocardiosis following ICI use.