Antithrombin III deficiency

Antithrombin III deficiency (abbreviated ATIII deficiency) is a deficiency of antithrombin III. This deficiency may be inherited or acquired. 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). Hereditary antithrombin deficiency results in a state of increased coagulation which may lead to venous thrombosis. Inheritance is usually autosomal dominant, though a few recessive cases have been noted. The disorder was first described by Egeberg in 1965. The causes of acquired antithrombin deficiency are easier to find than the hereditary deficiency.

This disease is affecting one in thousand people annually. It is type of multifactorial disease where both genetics and environment affect the procoagulant and anticoagulant forces, finally leading the ATIII deficiency. Various mutations in genes, such as deletion or addition of genes, for anticoagulant proteins such as protein C, antithrombin or protein S are one of the risk factors. The deficiency may be caused by adhesion of platelets with immobilised fibrinogen.

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.

Diagnosis

Different laboratory tests can be performed to investigate for antithrombin III deficiency. First, numerical analysis for antithrombin can be performed. A lower antithrombin III level increases the risk of venous thrombosis and pulmonary embolism. Second, Anticardiolipin antibodies (immunoglobulin G [IgG] and IgM class) can be injected. Third, antigen activity and total tests for Protein C and Protein S can be checked to see if the genes of their proteins have been mutated. Fourth, Prothrombin time (PT) and activated partial thromboplastin time (aPTT) can be calculated. Finally, Factor V Leiden test can also be performed in order to check blood clotting and adhesion of platelets.

Once a patient develops the congenital antithrombin III deficiency, a sign of anticoagulation can be easily indicated.

Image experiments can be studied to evaluate the antithrombin III deficiency. First of all, echocardiography is performed to all patients suffering from antithrombin III deficiency. These patients will be first go through the blood test to find a sign go arterial thrombus, then echocardiography can be tested. Second, doppler ultrasonography is usually performed at the earlier stage than echocardiography to compress. It is used to find the resolution of an acute thrombus. Finally, ventilation-perfusion scanning is test to check for images of pulmonary thrombosis.

Management

Heparin enhances ATIII activity and neutralizes "activated serine protease coagulation factors." 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 metabolism, so giving vitamin K1 (Phytonadione) will not reverse the effects of heparin.

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

See also

• Antithrombin

External links

Classification	ICD-10: D68.8 ICD-9-CM: 289.81 OMIM: 613118 MeSH: D020152 DiseasesDB: 783
External resources	eMedicine: ped/119