Abstract
Drug-related pneumonitis (DRP) caused by epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) is a fatal adverse event in patients with EGFR-mutant non-small cell lung cancer (NSCLC). The diagnosis of DRP is based on radiological findings, the temporal association of presentation with the initiation of a systemic therapeutic agent, and the exclusion of other likely causes. Here we report a case in which severe adenoviral pneumonia mimicking DRP occurred during treatment with osimertinib, and osimertinib was successfully resumed after recovery from adenoviral pneumonia.