Multiple organ infection and the pathogenesis of SARS

Gu, Jiang; Gong, Encong; Zhang, Bo; Zheng, Jie; Gao, Zifen; Zhong, Yanfeng; Zou, Wanzhong; Zhan, Jun; Wang, Shenglan; Xie, Zhigang; Zhuang, Hui; Wu, Bingquan; Zhong, Haohao; Shao, Hongquan; Fang, Weigang; Gao, Dongshia; Pei, Fei; Li, Xingwang; He, Zhongpin; Xu, Danzhen; Shi, Xeying; Anderson, Virginia M.; Leong, Anthony S.-Y.

The affected lungs showed severe consolidation with tissue consistency approximating that of the liver (Fig. 1 A) . The SARS lungs were, on average, three to four times heavier than normal lungs. Conventional light microscopy (LM) demonstrated widespread damage of the lung parenchyma, with extensive fibrin exudate, edema, interstitial thickening, and extensive hyaline membrane formation (Fig. 1 B) . There was extensive alveolar collapse, and the remaining alveoli were filled with fluid and desquamated alveolar and bronchial epithelial cells. Alveolar epithelial hyperplasia was evident. Large syncytial cells with multiple nuclei were present. Small vessel vasculitis was seen. However, cellular infiltrate was rare and conspicuously absent in most cases, and lymphocytic infiltration was sparse. Overall, the diffuse alveolar damage resembled that seen in adult respiratory distress syndrome, but with a paucity of inflammatory infiltrate.