A case report of pulmonary nocardiosis during pembrolizumab: the emerging challenge of the infections on immunotherapy.

The increasing occurrence of infectious complications during immune checkpoint inhibitor (ICI) therapy is an emerging challenge for oncologists. ICIs can reverse T-cell exhaustion, and this may lead to hyperinflammatory dysregulated immunity with subsequent potentially fatal infections. Nocardia spp. are opportunistic pathogens belonging to aerobic Actinomycetes. The authors report a case of Nocardia pneumonia in a 62-year-old male with oral squamous cell carcinoma and lung cancer while taking pembrolizumab. The patient did not take corticosteroids or other immunosuppressant medications. Since ICIs are able to stimulate the immune response, the authors hypothesize that immune reconstitution inflammatory syndrome due to pembrolizumab might cause this opportunistic infection.