Congenital antithrombin III deficiency

Definition

Congenital antithrombin III deficiency is a genetic disorder that causes the blood to clot more than normal.

Alternative Names

Deficiency - antithrombin III - congenital; Antithrombin III deficiency - congenital

Causes, incidence, and risk factors

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.

Symptoms

Patients will usually have symptoms of a blood clot, including:

• Coughing up blood
• Fainting
• Shortness of breath and pain when taking deep breaths
• Swelling of one leg

Signs and tests

A physical examination may show:

• A fast heart rate
• A swollen foot or ankle

The diagnosis is made by checking for low levels of antithrombin III in the patient's blood.

Treatment

A blood clot is treated with blood thinning medications or 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.

Expectations (prognosis)

Most patients have a good outcome if they stay on anticoagulant medications.

Complications

Blood clots can cause death, especially if they are in the lungs.

Calling your health care provider

See your health care provider if you have symptoms of this condition.

Prevention

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.

References

Schafer A. Thrombotic disorders: Hypercoagulable states. In: Goldman L, Ausiello D. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 182.