antithrombin III deficiency

What is Antithrombin III Deficiency?

Antithrombin III (ATIII) deficiency is a rare genetic disorder that affects the blood's ability to clot. It is characterized by a low level of antithrombin, a protein that helps regulate blood clotting.

• Causes: ATIII deficiency can be inherited or acquired due to various factors such as liver disease, kidney disease, or heparin therapy [1].
• Symptoms: People with this condition are at an increased risk for deep vein thrombosis (DVT) and pulmonary embolism (PE), which can lead to serious complications [2].
• Risk Factors: The combination of hereditary ATIII deficiency and other inherited disorders of blood clotting can increase the risk of developing abnormal blood clots [3]. Women with this condition are also at a higher risk of developing DVT during pregnancy or soon after delivery [4].

Types of Antithrombin III Deficiency

There are two categories of ATIII deficiency, classified based on plasma antigen levels:

• Type I (Classic) Deficiency: The majority of families affected by ATIII deficiency belong to this group, characterized by low levels of antithrombin in the blood [5].
• Other Categories: There may be other subtypes or variations of ATIII deficiency not yet fully understood or classified.

Prevalence and Impact

ATIII deficiency is a rare condition, affecting approximately 1 in 2,000 to 5,000 people worldwide. It can have significant implications for individuals with this condition, including an increased risk of venous and arterial thrombosis [6].

References:

[1] Context result 9 [2] Context result 11 [3] Context result 5 [4] Context result 11 [5] Context result 15 [6] Context result 13

Diagnostic Tests for Antithrombin III Deficiency

Antithrombin III (AT III) deficiency is a blood clotting disorder that requires accurate diagnosis to ensure proper management and treatment. Several diagnostic tests can help identify AT III deficiency, which are discussed below:

• Activity Assay: The recommended initial test for antithrombin deficiency is an activity (functional) assay. This test measures the functional level of antithrombin in the blood, providing a clear indication of whether the protein is functioning properly or not.
• Antigen Test: If the activity level is low, an antigen test is performed to determine the quantity of antithrombin present. This test measures the amount of antithrombin protein produced by the body, regardless of its functional ability.
• Activity-to-Antigen Ratio: When the activity level is low, a ratio between the activity and antigen levels can be calculated. This ratio helps in determining whether the deficiency is inherited or acquired.
• Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT): These tests are used to evaluate the coagulation pathway and can provide additional information about the presence of AT III deficiency.

Key Points

• The activity assay is the recommended initial test for antithrombin deficiency.
• An antigen test may be performed if the activity level is low.
• The activity-to-antigen ratio can help determine whether the deficiency is inherited or acquired.
• PT and aPTT tests can provide additional information about the coagulation pathway.

References

1. [6] The recommended initial test for antithrombin is an activity (functional) assay.
2. [10] Deficiency of antithrombin (AT; antithrombin III) can be inherited or acquired; it is defined as an AT activity level that is consistently less than 80 percent of normal (or the lower limit of the assay's reference range).
3. [11] A diagnostic algorithm for hereditary antithrombin deficiency, using functional assays and, if needed, antigen assays.
4. [12] Hereditary antithrombin deficiency is a hypercoagulable state associated with an increased risk for venous thrombosis.

These tests are crucial in diagnosing AT III deficiency accurately, ensuring that patients receive the appropriate treatment and management for their condition.

Differential Diagnosis of Antithrombin III Deficiency

Antithrombin III (ATIII) deficiency is a blood clotting disorder that can be challenging to diagnose, as it may present with similar symptoms to other conditions. Therefore, it's essential to consider the differential diagnosis when evaluating patients for ATIII deficiency.

Conditions to Consider in Differential Diagnosis:

• Factor V Leiden mutation: This genetic mutation increases the risk of blood clots and is often associated with deep vein thrombosis (DVT) and pulmonary embolism (PE).
• Protein C deficiency: Similar to ATIII deficiency, protein C deficiency can also lead to an increased risk of blood clots.
• Protein S deficiency: This condition can also contribute to the development of DVT and PE.
• Prothrombin gene mutation: A genetic mutation that increases the risk of blood clots.
• Disseminated intravascular coagulation (DIC): A serious medical condition characterized by widespread clotting in small blood vessels throughout the body.
• Antiphospholipid antibody syndrome (APS): An autoimmune disorder that can increase the risk of blood clots.

Additional Considerations:

• Catastrophic antiphospholipid syndrome (CAPS): A rare and severe form of APS that can lead to widespread clotting in small blood vessels.
• Thrombophilia: A term used to describe a condition characterized by an increased risk of blood clots, which can be caused by various factors, including genetic mutations or acquired conditions.

Key Points to Remember:

• ATIII deficiency is a rare genetic disorder that increases the risk of blood clots.
• Differential diagnosis is crucial when evaluating patients for ATIII deficiency, as other conditions may present with similar symptoms.
• A comprehensive evaluation, including laboratory tests and medical history, is essential to accurately diagnose ATIII deficiency.

References:

[3] Egeberg, O. (1965). Antithrombin III deficiency. [number1]

[4] Dahlbäck, B. (1993). Activated protein C resistance in 1993. [number10]

[8] Nygaard, K., & Brown, J. R. (1937). Thrombophilia: A term first coined by Nygaard and Brown in 1937. [number13]

Note: The numbers in square brackets refer to the corresponding references in the provided context.