Pathology: Grossly, lesions of MHV infection in immunocompetent mice occur infrequently. Lesions, when present, may include gaseous distention of the intestinal tract in suckling mice, and multiple white liver foci in older mice. The liver may have a hobnail, nodular appearance (B.).
Histopathologic examination of the intestinal tract reveals transient syncytia (arrowhead, A.) of the mucosal epithelial cells in mice infected with enterotropic virus strains. Focal coagulative liver necrosis can be seen in mice infected with polytropic virus strains (B.). Hepatocellular syncytia are rarely present around necrotic foci in immunocompetent mice (arrowhead, C.). In immunodeficient mice, intestinal epithelial cells, hepatocytes and vascular endothelial cells undergo syncytial cell formation, necrosis and replacement with scarring in certain organs, especially liver.