title: Clinicopathological findings of four cases of pure influenza virus A pneumonia.
abstract: OBJECTIVE
  The purpose of this study was to perform clinicopathological evaluations of patients with pure influenza A virus pneumonia.
  
  
  METHODS
  We performed clinicopathological analyses of four cases of pure influenza A virus pneumonia. Patients Among the four cases, three were caused by the pandemic (H1N1) 2009 virus. Three patients were analyzed during autopsy, and one underwent transbronchial lung biopsy.
  
  
  RESULTS
  We suggest that the interval between influenza virus A pneumonia onset and our analysis affected the pathological findings. Diffuse alveolar damage was observed during the acute phase. After ten days, organizing pneumonia and marked proliferation of premature type II alveolar epithelium were observed. Clinically, intra-alveolar hemorrhage was observed in two patients. Pathologically, hyaline membrane formation and intra-alveolar hemorrhage were observed in all cases.
  
  
  CONCLUSIONS
  Severe epithelial damage was determined as the main mechanism of respiratory failure caused by influenza A virus pneumonia.
authors.affiliation: Department of Infectious, Respiratory, and Digestive Medicine, Control and Prevention of Infectious Diseases (The First Department of Internal Medicine), Faculty of Medicine, University of the Ryukyus, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Fujita
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ohtsuki
authors.forename: Hajime
authors.initials: H
authors.lastname: Higa
authors.forename: Masato
authors.initials: M
authors.lastname: Azuma
authors.forename: Takeo
authors.initials: T
authors.lastname: Yoshinouchi
authors.forename: Shusaku
authors.initials: S
authors.lastname: Haranaga
authors.forename: Futoshi
authors.initials: F
authors.lastname: Higa
authors.forename: Masao
authors.initials: M
authors.lastname: Tateyama
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D001344:Autopsy; D001706:Biopsy; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000473:pathology* / Q000628:therapy / Q000821:virology; D008168:Lung / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011024:Pneumonia, Viral / Q000473:pathology* / Q000628:therapy / Q000821:virology; D055815:Young Adult