Portal vein thrombosis caused by protein C and protein S deficiency associated with cytomegalovirus infection.

A 4-month-old girl who was examined because of splenomegaly had portal vein thrombosis, which apparently resulted from a combination of cytomegalovirus infection and deficiency of both protein S and protein C. The cytomegalovirus infection, by damaging endothelial cells, may have triggered a cascade of events that was ultimately expressed as portal vein thrombosis resulting from deficiency of proteins S and C.