Acute progression of aspergillosis in a patient with lung cancer receiving nivolumab

A 65‐year‐old man with chronic progressive pulmonary aspergillosis (CPPA) was admitted for the treatment of lung adenocarcinoma while receiving an immune checkpoint inhibitor, nivolumab. The tumour responded well to the therapy, but the cavity of CPPA became large in contrast to the tumour after 20 courses of therapy. He was diagnosed as having exacerbation of CPPA and successfully and concurrently treated with an antifungal agent and nivolumab. Since there was absence of obvious immunosuppression and the presence of a drastic effect on tumour remission during nivolumab therapy, this phenomenon suggested that the trigger of CPPA progression was dependent not on immunosuppression but on a hyperreaction to microorganisms, which was similar to the immune reconstitution inflammatory syndrome caused by nivolumab. This was a thought‐provoking case in which the immune checkpoint inhibitor had a paradoxical effect for the tumour and infection.