"Patients with heterozygous protein C deficiency usually are asymptomatic until after puberty. At this time, patients may experience spontaneous thrombosis or thrombosis subsequent to a predisposing risk factor. The frequency and extent of thrombosis are highly variable, and a careful family history of thrombotic disease is essential whenever possible. Familial studies of sequelae in protein C deficiency reveal that individuals likely experienced undiagnosed thrombotic events."

Protein C deficiency can be readily diagnosed by laboratory testing. Anyone with a family history of thrombotic events should be tested.