Protein C or protein S deficiency is also sometimes suspected when a venous thromboembolism develops in an unusual site like the portal, mesenteric, or cerebral veins.
A more serious presentation is neonatal purpura fulminans, which is when a newborn with protein C or S deficiency suffers massive arterial and venous thromboembolisms with hemorrhagic skin necrosis.
Another UK study published last year found incidences of and deaths from thromboembolism doubled in the first six months of the pandemic compared to rates seen in the years prior.
Protein C or S deficiency is suspected in people with a strong family history of coagulation disorders, especially those who suffer from recurrent venous thromboembolisms and experience their first thrombotic event before age fifty.