Fatalities of Novel H1N1 Influenza Virus Display Diffuse Alveolar Damage, Peripheral Pulmonary Thrombosis, and Cytophagocytosis
PW Harms, LB Smith, JL Myers, JM Jentzen. University of Michigan Health Systems, Ann Arbor, MI
Background: A novel pandemic strain of H1N1 influenza A virus emerged in the spring of 2009. The histopathologic features of severe infection with novel H1N1 influenza virus have not been described.
Design: We retrospectively reviewed medical records and autopsy findings from four patients who died from novel H1N1 influenza virus infection. H1N1 influenza virus was confirmed by PCR conducted on ante mortem and/or autopsy specimens. All patients were managed with extracorporeal membrane oxygenation (ECMO). We also reviewed autopsies from 8 age and sex-matched control patients without H1N1 infection who were managed with ECMO.
Results: All patients were men, age 28–57 years (mean 44.8 ± 12.6 years). Disease course varied from 16 to 38 days. One patient had culture-proven respiratory bacterial superinfection during hospitalization. Diffuse alveolar damage (DAD) affected all influenza patients, compared to 50% of the control group. Concomitant acute bronchopneumonia was present in two influenza patients, including one with bacterial superinfection. Thrombosis of peripheral pulmonary vasculature occurred in three influenza patients, with infarcts in one. Peripheral thrombosis was also seen in three controls. Cytophagocytosis, a feature of hemophagocytic syndrome, was present in bone marrow, spleen, and lymph node in four, one and one influenza patients, respectively. The extent of involvement was variable. The diagnosis of hemophagocytic syndrome could not be established with certainty on the clinical and laboratory data available after death; however, all of the patients met 3-4 clinical criteria. Cytophagocytic cells were seen in two of the control cases, including one patient who died of a possible viral pneumonia.
Conclusions: Lung involvement in severe novel H1N1 infection is characterized by thrombosis, hemorrhage and DAD. Hemophagocytic syndrome, which has been associated with other viral illnesses including influenza, may contribute to the severe infection seen in a subset of patients. Careful clinical evaluation to assess for the presence of hemophagocytic syndrome is recommended.
Monday, March 22, 2010 1:00 PM
Platform Session: Section G, Monday Afternoon