Protein C deficiency is...

Protein C deficiency is...

• A. Protein C is a vitamin K–dependent anticoagulant produced by the liver
• B. Protein C deficiency causes increased platelet production
• C. Protein C deficiency is an autosomal recessive disorder
• D. Protein C promotes coagulation by activating Factor V

Answer: (A)

Protein C is a vitamin K–dependent anticoagulant produced by the liver. When activated on the endothelium (by thrombin bound to thrombomodulin), activated Protein C inactivates Factors Va and VIIIa, limiting thrombin generation and slowing clot formation. Deficiency of Protein C removes this natural brake, increasing the risk of unopposed coagulation and venous thrombosis. This statement is true about Protein C itself, whereas the other options describe effects or inheritance patterns that don’t fit Protein C’s role: it does not increase platelet production, it is not typically autosomal recessive (most hereditary cases are autosomal dominant), and it does not promote coagulation.

Protein C is a vitamin K–dependent anticoagulant produced by the liver. When activated on the endothelium (by thrombin bound to thrombomodulin), activated Protein C inactivates Factors Va and VIIIa, limiting thrombin generation and slowing clot formation. Deficiency of Protein C removes this natural brake, increasing the risk of unopposed coagulation and venous thrombosis. This statement is true about Protein C itself, whereas the other options describe effects or inheritance patterns that don’t fit Protein C’s role: it does not increase platelet production, it is not typically autosomal recessive (most hereditary cases are autosomal dominant), and it does not promote coagulation.