Hantavirus pulmonary syndrome is distinguishable from acute interstitial pneumonia

Context. - Hantavirus pulmonary syndrome (HPS) and acute interstitial pneumonia (AIP) can share similar clinical presentations. AIP is an acute, diffuse lung disease that has some clinical features suggesting a viral infection, although causative agent(s) have not been identified. Objective. - To clinically, histologically, and immunohistochemically compare cases of HPS to cases of AIP and to determine if any cases of AIP were actually examples of HPS. Design. - Seven cases of HPS and 9 cases of AIP were compared clinically and histologically by semiquantitative grading of features in lung tissue. The cases were also evaluated immunohistochemically for the presence of hantaviral antigens. Results. - Hantavirus pulmonary syndrome had a shorter clinical duration and more acute changes histopathologically; AIP was of longer clinical duration and was usually accompanied by histologic evidence of organization. Hantavirus pulmonary syndrome was distinguished by the presence of immature leukocytes in the pulmonary vasculature. No hantaviral antigens were identified immunohistochemically in the 9 case of AIP. Hantaviral antigens were identified in all 7 cases of HPS. Conclusion. - Cases of AIP and fatal cases of HPS can generally be distinguished on clinical and histologic grounds, and this distinction can be further confirmed immunohistochemically.