Abstract We encountered a patient with severe coronavirus disease 2019 (COVID‐19)‐related pneumonia, who died of progressive respiratory acidosis after 2 months of treatment with mechanical ventilation. The autopsy revealed diffuse alveolar damage (DAD) without any active signs of fungal or bacterial infections, suggesting prolonged and over‐activated immune responses against COVID‐19 infection. When COVID‐19 patients develop acute respiratory distress syndrome, it is essential to remember that the infection can progress to DAD a few months after the disease onset.