Reduced protein S activity

What it means

An abnormality of coagulation related to a decreased concentration of vitamin K-dependent protein S. Protein S is a cofactor of protein C.

Protein S functions as a cofactor to Protein C in the inactivation of Factors Va and VIIIa in the coagulation pathway. Therefore, a defect in protein S is associated with an increased risk of thrombosis.

Rare diseases that can present with this9

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Protein S deficiency