What is Factor XII Deficiency?
This disease is considered to be a rather rare violation of coagulation hemostasis. For the first time pathology was revealed by O. Ratnov in 1964.
The disease is characterized by a strong decrease in the activity of the trigger factor of the internal mechanism of blood coagulation – factor XII.
Factor XII (Hageman factor) – collagen-activated sialoglycoprotein is a natural activator of both the coagulant and kallikrein-kinin and fibrinolytic systems.
Causes of Deficit Factor XII
In most cases, the Hageman defect is inherited in a recessive-autosomal type. However, in some families, autosomal dominant inheritance has been identified. Apparently, the synthesis of factor XII is controlled by two autosomal genes (bimodal inheritance).
Even earlier, such a conclusion was made by a number of authors on the basis that the recessive transmitters of the Hageman defect are divided into groups with low and higher content of factor XII in plasma.
Immunological studies indicate that both forms of the Hagemann defect (recessively and dominantly inherited) are characterized by reduced synthesis of this protein, and not the formation of its abnormal molecules.
Symptoms of Deficit Factor XII
With a deficiency of factor XII, there are no hemorrhagic events (not only spontaneous, but also with injuries), despite the pronounced lengthening of the blood coagulation time – up to 30 minutes or more.
A number of hypotheses were put forward to explain this paradoxical phenomenon: the ability of tissue extracts and platelets to cover the deficit of factor XII and partly the PTA is noted.
The lack of fibrinolysis explains that a number of patients with Hagemann defect, despite a sharp slowdown in blood clotting, have severe and even fatal thromboembolic complications, including pulmonary embolism after a fracture of the pelvic bones in the first identified carrier of this defect, Hagemann.
At this defect, myocardial infarction and thrombophlebitis in the newborn were also observed.
There is a strict correspondence between the degree of coagulation disorder and the Hageman factor deficiency: with pronounced hypocoagulation, the level of this factor in plasma does not exceed 2% and more often less than 1%; with moderate coagulation disorders, it varies from 3 to 9%.
In cases where the concentration of factor XII in plasma is 10% or more, blood clotting, activated partial thromboplastin time and other tests are normalized.
Diagnosis of Defecit Factor XII
The Hageman defect should be suspected in cases where there is a significant increase in blood clotting time, accompanied by the absence of bleeding or a slight severity. However, the most complete argumentation of the diagnosis is achieved by mixing tests with plasma taken from patients with a deficiency of factor XII and other factors, as well as an immunological determination in the plasma of a patient of factor XII.
A peculiar form of factor XII deficiency with moderately pronounced hemorrhagic syndrome (mild bruising, bleeding during operations, injuries, sometimes during childbirth), various allergic syndromes (angioedema, bronchial asthma, eczema) and a high incidence of early cerebral strokes were detected in 1970. Unlike the usual Hageman defect, this form is inherited in an incomplete dominant type.
Defecit Factor XII Treatment
Most patients with factor XII deficiency do not need replacement therapy or special preoperative preparation. Small transfusions of donor plasma cause in patients with Hagemann defect complete normalization of the coagulogram. The half-life of factor XII introduced into the bloodstream is about 48-56 hours.
If there is no full confidence in the correctness of the diagnosis or the patient (his relatives) had any bleeding before, then the doctor prescribes a plasma transfusion before the surgery. Transfusion therapy is carried out in the same way as for factor XI deficiency.
In case of Hageman defect, aminocaproic acid and other fibrinolysis inhibitors should not be used, since this pathology is accompanied by insufficiency of the fibrinolytic system. In this situation, the appointment of antifibrinolytics increases the risk of thromboembolism.