Figure 2.

Histologic and ultrastructural appearances of the colon in a patient with SARS-CoV infection. (A) Endoscopic colonic biopsy specimens with scattered lipofusin-ladened macrophages in the lamina propria indicative of melanosis coli. The macrophages are indicated by the red arrows, and there were no significant inflammatory cell infiltrates (H&E; original magnification 200×). (B) Dilated cytoplasmic vesicles, which were consistent with dilated endoplasmic reticulum, were seen toward the apical cytoplasm (indicated by red arrowheads) and some were filled with viral particles. A number of viral particles were also seen on the surface microvilli (indicated by black arrows). (C) Higher magnification of the virus-containing vesicles. The viral particles had mild variation in size and ranged from 60 to 90 nm in dimension, which is consistent with coronavirus morphologically. (D) Viral particles were detected on the luminal surface of the enterocytes. Some viral particles appeared to attach onto the microvilli, whereas some appeared to be detached from the cell.