Antithrombin Deficiency (Congenital)

Definition

Definition of Antithrombin Deficiency (Congenital)
Antithrombin III (ATIII) is a potent inhibitor of the coagulation cascade. It is a nonvitamin K-dependent protease that inhibits coagulation by lysing thrombin and factor Xa. Antithrombin III activity is markedly potentiated by heparin; potentiation of its activity is the principle mechanism by which both heparin and low molecular weight heparin result in anticoagulation.

Congenital antithrombin III deficiency is an autosomal dominant disorder in which an individual inherits one copy of a defective gene. This condition leads to increased risk of venous and arterial thrombosis, with an onset of clinical manifestations typically appearing in young adulthood. This form is commonly diagnosed during childhood by screening after an affected family member has been identified or after a child has had a thrombotic event.

Symptoms

Symptoms of Antithrombin Deficiency (Congenital)
Patients will usually have symptoms of a blood clot, including:

1. Coughing up blood
2. Fainting
3. Shortness of breath and pain when taking deep breaths
4. Swelling of one leg

Causes

Causes of Antithrombin Deficiency (Congenital)
Antithrombin III is a protein in the blood that naturally blocks blood clots from forming. Congenital antithrombin III deficiency is an inherited disease. It occurs when a person receives one abnormal copy of a gene from a parent with the disease.

The abnormal gene leads to low levels of antithrombin III. These low levels of antithrombin III can cause abnormal blood clots (thrombi) that may damage organs.

Often, patients with this condition will have a blood clot at a young age and will have a family member who has also experienced a blood clotting episode. In people with this condition, a blood clot may occur without the common risk factors of pregnancy, lack of movement (due to surgery or trauma), or use of oral birth control pills.

Diagnosis

Diagnosis of Antithrombin Deficiency (Congenital)
A physical examination may show:

1. Abnormal lung sounds
2. Fast breathing
3. Fast heart rate
4. Swollen foot or leg

Treatment

Treatment of Antithrombin Deficiency (Congenital)
A blood clot is treated with blood thinning medications (also called anticoagulants). How long you need to take these medications depends on how serious the blood clot was and other factors. Discuss this with your health care provider.

Prognosis

Prognosis of Antithrombin Deficiency (Congenital)
Most patients have a good outcome if they stay on anticoagulant medications.

Prevention

Prevention of Antithrombin Deficiency (Congenital)
Because this is an inherited condition, there is no way to prevent it. However, once a patient is diagnosed with antithrombin III deficiency, all close family members should be screened.