Hereditary thrombophilia due to congenital antithrombin deficiency

What it is

From: Orphanet

Hereditary thrombophilia due to congenital antithrombin deficiency is a rare, genetic, hematological disease characterized by decreased levels of antithrombin activity in plasma resulting in impaired inactivation of thrombin and factor Xa. Patients have an increased risk for venous thromboembolism, usually in the deep veins of the arms, legs and pulmonary system and, on occasion, in other venous territories (e.g. cerebral veins or sinus, mesenteric, portal, hepatic, renal and/or retinal veins).

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Reduced antithrombin III activity · Very frequent (99-80%)

An abnormality of coagulation related to a decreased concentration of antithrombin-III.

Reduced antithrombin antigen · Very frequent (99-80%)

Reduced antithrombin antigen. A reduced level of antithrombin may lead to an increased risk of thrombus formation.

Deep venous thrombosis · Frequent (79-30%)

Formation of a blot clot in a deep vein. The clot often blocks blood flow, causing swelling and pain. The deep veins of the leg are most often affected.

Pregnancy exposure · Frequent (79-30%)

Exposure of pregnant women to toxins from any source, such as environmental toxins or chemicals, that may potentially cause problems such as miscarriage, preterm delivery, low birth weight, and, in some cases, developmental delays in infants.

Pulmonary embolism · Frequent (79-30%)

An embolus (that is, an abnormal particle circulating in the blood) located in the pulmonary artery and thereby blocking blood circulation to the lung. Usually the embolus is a blood clot that has developed in an extremity (for instance, a deep venous thrombosis), detached, and traveled through the circulation before becoming trapped in the pulmonary artery.

Recurrent thromboembolism · Frequent (79-30%)

Repeated episodes of obstruction of blood flow due to an embolus, i.e., blood clot that has traveled from its point of origin within the blood stream.

Superficial thrombophlebitis · Frequent (79-30%)

Inflammation of a superficial vein associated with venous thrombosis (blood clot formation within the vein).

Arterial thrombosis · Occasional (29-5%)

The formation of a blood clot inside an artery.

Hepatic vein thrombosis · Occasional (29-5%)

An obstruction in the veins of the liver caused by a blood clot (thrombosis).

Mesenteric venous thrombosis · Occasional (29-5%)

A clot that obstructs blood flow in a mesenteric vein (the superior and the inferior mesenteric vein drain blood from the small and large intestine).

Portal vein thrombosis · Occasional (29-5%)

Thrombosis of the portal vein and/or its tributaries, which include the splenic vein and the superior and inferior mesenteric veins.

Recurrent spontaneous abortion · Occasional (29-5%)

Repeated episodes of abortion (Expulsion of the product of fertilization before completing the term of gestation) without deliberate interference.

Retinal vein occlusion · Occasional (29-5%)

Blockage of a retinal vein or venule, occurring typically at an arteriovenous crossing. Typically presenting with dilated veins, retinal hemorrhages and in some cases non-perfusion.

Spontaneous abortion · Occasional (29-5%)

A pregnancy that ends at a stage in which the fetus is incapable of surviving on its own, defined as the spontaneous loss of a fetus before the 22th week of pregnancy.

Other findings in the same source

From: Orphanet

Additional reported features include Cerebral venous thrombosis (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Adolescent; Adult

Inheritance in the source

From: Orphanet

Autosomal dominant

Frequency and the population described

From: Orphanet

Point prevalence: 1-5 / 10 000; Worldwide; Class only.

Understanding the inheritance label

From: MedlinePlus Genetics

An autosomal dominant pattern means that one altered copy of a relevant gene can be sufficient for the condition. Some affected people inherit the change; others have a new change without an affected parent. The precise finding, family history and condition determine what this means for relatives.

Which doctor should you see?

The suggested department for discussing Hereditary thrombophilia due to congenital antithrombin deficiency is Haematology, with a haematologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which blood-cell, marrow, bleeding or clotting finding matters most?
• Does the diagnosis need confirmation or a more precise subtype?
• Which symptoms or laboratory changes should trigger earlier review?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Hereditary thrombophilia due to congenital antithrombin deficiency. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.