Which coagulation disorder is characterized by a deficiency of protein S, leading to an increased risk of thrombosis?

A Protein C deficiency
B Protein S deficiency ✓
C Antithrombin III deficiency
D Factor V Leiden mutation

Explanation

Protein S is a vitamin K-dependent protein that plays a crucial role in the regulation of coagulation. A deficiency of protein S can lead to an increased risk of thrombosis due to the unregulated activity of factors Va and Xa.

Source

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