Histopathological autoptic findings in 8 patients with pandemic influenza A (H1N1) pneumonia.

Unlabelled: In the years 2009 and 2010 a novel influenza A (H1N1) caused the first influenza pandemic after 41 years. In the Czech Republic it culminated in November and December 2009 and there were 101 laboratory-confirmed deaths. Another few cases occurred later in the year 2010 and at the beginning of 2011. Here we report 8 autoptic cases of patients who died between 2009 and 2011 with confirmed H1N1 influenza and underwent a post mortem examination at the Institute of Pathology, General University Hospital in Prague, Czech Republic. This group differs from the others reported in literature by having a higher age as well as a higher percentage of patients with pre-existing severe comorbidities including malignant diseases. All 8 patients developed atypical pneumonia with subsequent respiratory failure. In this article we present these cases with related clinical data and findings in other organs, but we focus primarily on the findings in the respiratory tract which were shown to be approximately similar to those in the other studies and case reports. Nevertheless there were also some noteworthy variations. The most prominent feature observed was diffuse alveolar damage accompanied by intraalveolar haemorrhage and inflammatory infiltrate of variable extent. Less frequent features included cytopathic changes of pneumocytes and their desquamation, reactive changes of bronchial epithelium, intraalveolar fibrinous exudate, minor necroses, residual necrotizing bronchitis, focal granulation tissue and incipient fibrosis. In one case we found an extraordinary vascular change of uncertain origin. In conclusion, this group of patients is slightly atypical and differ in some features from those in other published studies and case reports concerning novel pandemic influenza. By reporting them we wish to extend the number of described cases, which may contribute to a better understanding of the pathogenesis of novel influenza infection.

Keywords: influenza A virus, subtype H1N1 - viral pneumonia - diffuse alveolar damage.