Immunohistochemical findings of an autopsied lung specimen from a patient with pandemic influenza (A/H1N1pdm) virus infection.

A 24-year-old female presented with fever and dry cough. Influenza A virus infection was suspected and the patient was treated with neuraminidase inhibitors. Five days after diagnosis, the patient developed persistent fever and dyspnea, and was diagnosed with severe pneumonia. Despite intensive treatment, the pneumonia worsened and the patient died 14 days after admission. At autopsy, a diffuse alveolar damage (DAD) pattern was observed. Immunohistochemical evaluation indicated severe epithelial damage, resulting in successive regeneration of alveolar type II cells followed by marked proliferation of smooth muscle cells and an increase of collagen fibers at the tip of alveolar orifices.