Most common type of inherited disease of hypercoagulobility is?
**Core Concept**
Antithrombin III deficiency is a type of inherited hypercoagulable state that increases the risk of thrombosis due to impaired anticoagulant activity. This deficiency affects the regulation of coagulation pathways, leading to excessive clot formation.
**Why the Correct Answer is Right**
The correct answer is Antithrombin III deficiency because it is the most common inherited hypercoagulable state. Antithrombin III is a protein that inhibits the activity of thrombin and other clotting factors, thereby preventing excessive clot formation. A deficiency in antithrombin III results in an imbalance between procoagulant and anticoagulant pathways, increasing the risk of venous thromboembolism.
**Why Each Wrong Option is Incorrect**
* **Option A:** Factor V Leiden mutation is a common cause of inherited hypercoagulability, but it is not the most common type. Factor V Leiden is a procoagulant mutation that increases the risk of thrombosis by making factor V resistant to inactivation by activated protein C.
* **Option B:** Protein C deficiency is another inherited hypercoagulable state, but it is less common than antithrombin III deficiency. Protein C is an anticoagulant protein that inhibits the activity of factor Va and factor VIIIa.
* **Option D:** Prothrombin G20210A mutation is a rare inherited hypercoagulable state that increases the levels of prothrombin, a key clotting factor. While it is a significant risk factor for thrombosis, it is not as common as antithrombin III deficiency.
**Clinical Pearl / High-Yield Fact**
Antithrombin III deficiency is often asymptomatic until a thrombotic event occurs, making it essential to consider this diagnosis in patients with unexplained venous thromboembolism.
**Correct Answer: C. Antithrombin III deficiency.**