An adult autopsy case of acute encephalopathy associated with influenza A virus.

On a cold winter morning, a 35-year-old male was unexpectedly found dead and therefore autopsied. Macro- and microscopically, the lungs were demonstrated bronchopneumonia. On the surface of brain, small blood vessels were slightly congested. Microscopically, brain edema was also observed, and proliferation of lymphocytes was observed around the capillary vessels of the hippocampus. These findings suggested a viral infection of the cerebrum. We conducted an immunohistochemical study with antibody against influenza virus. Influenza A virus antigen was detected in both the lungs and brain. Therefore, findings were compatible with influenza A encephalopathy. Even when serological inspection is not performed, it is useful to inspect localization of the virus antigen immunohistochemically. We considered that it is necessary to perform pathological examination for influenza encephalopathy in sudden death cases when influenza is epidemic.