Question 1

What is the Meaning of Activated Protein C Resistance?

Accepted Answer

Activated Protein C Resistance describes a condition where the body's natural anticoagulant, Activated Protein C (APC), is less effective at inhibiting blood clotting. This impairment primarily stems from an altered response of key clotting factors, most commonly Factor V, to APC's regulatory action, leading to an increased propensity for thrombus formation.

Question 2

What is the Context of Activated Protein C Resistance?

Accepted Answer

This physiological state operates within the intricate hemostatic system, specifically impacting the delicate balance between coagulation and anticoagulation. Activated Protein C normally functions as a critical enzyme that downregulates clot formation by cleaving and inactivating procoagulant factors V and VIII, thus preventing excessive thrombosis.

Question 3

What is the Significance of Activated Protein C Resistance?

Accepted Answer

Clinically, Activated Protein C Resistance represents the most prevalent inherited risk factor for venous thromboembolism, including deep vein thrombosis and pulmonary embolism. Its identification is crucial for assessing an individual's thrombotic risk, guiding preventative strategies, and informing therapeutic decisions, particularly in situations that inherently increase clotting potential.

Question 4

What is the Mechanism of Activated Protein C Resistance?

Accepted Answer

The underlying mechanism typically involves a genetic alteration, predominantly the Factor V Leiden mutation, which substitutes an arginine for a glutamine at position 506 of Factor V. This specific amino acid change renders Factor V resistant to inactivation by Activated Protein C, allowing it to persist longer in its active procoagulant form and thus promote sustained thrombin generation.

Question 5

What is the Application of Activated Protein C Resistance?

Accepted Answer

In clinical practice, the presence of Activated Protein C Resistance is considered when evaluating patients with unprovoked or recurrent thrombotic events, or those with a family history of such conditions. Knowledge of this resistance helps clinicians tailor management, which may include prophylactic anticoagulation during high-risk periods like surgery, prolonged immobilization, or pregnancy, aiming to mitigate thrombotic complications.

Question 6

What is the Metric of Activated Protein C Resistance?

Accepted Answer

Assessment for Activated Protein C Resistance commonly begins with a functional assay, often an Activated Partial Thromboplastin Time (aPTT)-based test, which measures the prolongation of clotting time in the presence of exogenous APC. Definitive confirmation of the underlying genetic cause, specifically the Factor V Leiden mutation, is then achieved through molecular genetic testing of genomic DNA.

Question 7

What is the Risk of Activated Protein C Resistance?

Accepted Answer

The primary clinical risk associated with Activated Protein C Resistance is a significantly elevated lifetime risk of developing venous thromboembolism. This risk is further compounded by the presence of additional prothrombotic factors, such as hormonal therapy, certain surgical procedures, prolonged immobility, or other inherited thrombophilias, necessitating careful clinical consideration to prevent adverse thrombotic outcomes.

Activated Protein C Resistance

Meaning

Context

Significance

Mechanism

Application

Metric

Risk

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