Lung, Parainfluenza pneumonia

Parainfluenza is a paramyxovirus that can cause severe pneumonia in immunocompromised hosts and can be fatal particularly when complicated by diffuse alveolar damage or superimposed bacterial infection. In this case, the pattern is of giant-cell interstitial pneumonia with diffuse alveolar hemorrhage. These giant cells do not originate from macrophages, but from pneumocytes. Cytoplasmic eosinophilic viral inclusions can be seen.

This pattern of giant-cell pneumonia is not specific, and can be seen in a variety of infections (measles, parainfluenza, respiratory synctitial virus, varicella zoster) as well as pneumoconiosis secondary to inhalations of heavy metals. Measles tend to present with both intranuclear and cytoplasmic inclusions, while Varicella zoster would present with only nuclear inclusions. RSV can also present with cytoplasmic inclusions. PCR can provide a more specific diagnosis.