## **Core Concept**
The question pertains to a condition known as **Factor V Leiden thrombophilia**, which is associated with a mutation in the gene encoding **Factor V**. This mutation leads to an increased risk of thrombosis due to the production of a defective Factor V protein that is resistant to inactivation by **activated protein C (APC)**.

## **Why the Correct Answer is Right**
The correct answer, **. Factor V Leiden**, is right because the **Factor V Leiden** mutation results in a form of Factor V that cannot be properly regulated by APC. APC normally cleaves and inactivates Factor Va as part of the anticoagulant pathway. The mutation leads to a hypercoagulable state because the defective Factor V remains active, promoting coagulation. This condition increases the risk of venous thromboembolism.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify a known condition related to a defective Factor V gene.
- **Option B:** This option is incorrect as it does not relate to the specific condition caused by a defective Factor V gene leading to hypercoagulability.
- **Option D:** This option is incorrect because it does not accurately describe the condition associated with a mutation in the Factor V gene.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **Factor V Leiden** is a common inherited risk factor for venous thromboembolism. Individuals with this mutation are at increased risk of developing deep vein thrombosis and pulmonary embolism. The condition is more prevalent in individuals of European descent.

## **Correct Answer:** . Factor V Leiden