Is Antithrombin III deficiency hereditary?

Antithrombin III deficiency is a hereditary condition caused by mutations in the SERPINC1 gene, which regulates blood clotting. It follows an autosomal dominant inheritance pattern, meaning an affected parent has a 50% chance of passing the genetic mutation to each of their children.

Is Antithrombin III deficiency strictly hereditary?

Antithrombin III deficiency is primarily a hereditary (genetic) condition, meaning it is passed down through families via changes in the DNA. While the vast majority of cases are inherited from a parent, it is important to distinguish between "hereditary" and "genetic." A condition is genetic if it is caused by a mutation, and hereditary if that mutation is inherited from a parent. In rare instances, an individual may present with the condition due to a de novo mutation—a spontaneous change that occurs for the first time in the individual—rather than being inherited from a parent.

What is the inheritance pattern of Antithrombin III deficiency?

Antithrombin III deficiency is inherited in an autosomal dominant pattern. This means that only one copy of the altered SERPINC1 gene is necessary to increase the risk of developing the disorder. Because it is autosomal, the condition affects males and females equally. For an individual with Antithrombin III deficiency, the risk of passing the mutation to their offspring is 50% for each pregnancy, regardless of the child's sex.

How is Antithrombin III deficiency diagnosed genetically?

Genetic testing for Antithrombin III deficiency involves sequencing the SERPINC1 gene to identify pathogenic variants. Clinical geneticists generally recommend testing in the following scenarios:

• Individuals who have experienced unexplained venous thromboembolism (VTE), particularly at a young age or in unusual sites.


• Family members of a patient who has already been diagnosed with Antithrombin III deficiency.


• Individuals with a strong family history of recurrent blood clots or pregnancy complications.


• Patients who show persistently low functional antithrombin levels in routine blood coagulation screenings.

What is the role of genetic counseling for families?

Genetic counseling is a vital step for families affected by Antithrombin III deficiency. A genetic counselor can help interpret family history, explain the 50% recurrence risk, and discuss the implications of testing for asymptomatic relatives. For those planning a pregnancy, counseling provides an opportunity to discuss management strategies, as the risk of thrombosis increases significantly during gestation and the postpartum period. While prenatal diagnosis via amniocentesis or chorionic villus sampling is technically possible, it is rarely pursued for Antithrombin III deficiency due to the treatable nature of the condition and the availability of effective anticoagulation therapies for affected individuals.

Joining the community

At DiseaseMaps.org, we currently have 42 people with Antithrombin III deficiency who have joined our community. Sharing experiences with others who understand the unique challenges of managing this hereditary clotting disorder can provide significant emotional support and practical insights into living with the condition.

Next steps

• Consult with a hematologist or a clinical geneticist to discuss whether diagnostic testing is appropriate for you or your family members.


• Gather detailed medical records regarding any family history of deep vein thrombosis (DVT) or pulmonary embolism (PE).


• Connect with the 42 members of the DiseaseMaps.org community to learn how others manage the daily realities of living with Antithrombin III deficiency.


• Discuss pregnancy and surgical planning with your medical team well in advance to ensure appropriate prophylactic anticoagulation measures are in place.

Medical disclaimer: This information is for educational purposes only and does not replace professional medical advice, diagnosis, or treatment; always seek the guidance of your physician regarding any medical condition.

References

• NIH Genetic and Rare Diseases (GARD) Information Center: Antithrombin deficiency.


• Orphanet: Hereditary antithrombin deficiency (ORPHA:93966).


• OMIM (Online Mendelian Inheritance in Man): Antithrombin III deficiency (#613118).


• National Blood Clot Alliance (NBCA): Information on inherited thrombophilias.