Pulmonary Nocardiosis in a Non-Small Cell Lung Cancer Patient Being Treated for Pembrolizumab-Associated Pneumonitis

To our knowledge, this represents the second known case of pulmonary nocardiosis in a patient on pembrolizumab. Moreover, this is a rarely reported instance of opportunistic bacterial infection following steroid treatment for ICI pneumonitis. This case report emphasizes the risk of bacterial infection associated with ICI pneumonitis, both due to the difficulty of excluding underlying infection at presentation, and the immunosuppression caused by irAE treatment. As such, we suggest that clinicians maintain a high suspicion for potential infection in ICI pneumonitis, and strongly consider initiating infectious workup with regular follow-ups for monitoring. Prophylactic antibiotics could be considered when such monitoring is not possible.