Antithrombin III deficiency

Antithrombin III deficiency (abbreviated ATIII deficiency) is a deficiency of antithrombin III. It is a rare hereditary disorder that generally comes to light when a patient suffers recurrent venous thrombosis and pulmonary embolism, and repetitive intrauterine fetal death (IUFD).^[1] Inheritance is usually autosomal dominant, though a few recessive cases have been noted.^[2]

The disorder was first described by Egeberg in 1965.^[3]

The patients are treated with anticoagulants or, more rarely, with antithrombin concentrate.

In kidney failure, especially nephrotic syndrome, antithrombin is lost in the urine, leading to a higher activity of Factor II and Factor X and in increased tendency to thrombosis.

Heparin resistance

Heparin enhances ATIII activity and neutralizes "activated serine protease coagulation factors."^[4] Patients with ATIII deficiency requiring anticoagulant therapy with heparin will need higher doses of heparin. ATIII binds to thrombin and then forms the thrombin-anti thrombin complex or TAT complex. This is a major natural pathway of anticoagulation. This binding of thrombin to AT is greatly enhanced in the presence of heparin. Heparin does not affect vitamin K epoxide, an enzyme required for the reduction of vitamin K, so giving vitamin K1 (Phytonadione) will not reverse the effects of heparin. ^[5]

Heparin is used in bridge therapy when initiating a patient on warfarin when in a hospital setting. It can be used in DVT prophylaxis and treatment, acute coronary syndromes, and ST-segment elevated MI.

See also

• Antithrombin

References

External links

• Information on antithrombin from UIUC
• Non-profit advocacy group for patients and families with antithrombin deficiency