A patient with a history of deep vein thrombosis is found to have a mutation in the gene encoding antithrombin III. What is the likely consequence of this mutation?

A Increased risk of bleeding due to impaired fibrinolysis
B Decreased risk of thrombosis due to enhanced anticoagulant activity
C Increased risk of thrombosis due to impaired inhibition of coagulation factors ✓
D Impaired platelet function leading to easy bruising

Explanation

Antithrombin III is a natural anticoagulant that inhibits several coagulation factors, including thrombin and factor Xa. A mutation in the gene encoding antithrombin III can lead to impaired anticoagulant activity, resulting in an increased risk of thrombosis.

Source

Harrison's Principles of Internal Medicine
Hematology Hematology: Coagulation Disorders Hematology: Coagulation Disorders Hard MEDICAL Confidence: high