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At a Glance

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Inherited coagulation disorder caused by a deficiency in plasma protein factor XII (FXII) characterized by in vitro delayed blood clotting without a clinical bleeding tendency. The condition may also be acquired and temporary.

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Synonyms

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Factor XII Deficiency; HAF Deficiency; Hageman Trait.

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History

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Coagulation disorder first described in 1955 after routine preoperative laboratory examination of a patient named John Hageman.

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Incidence

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From 1955 to 2002, only a few hundred reported cases. Incidence is greater in patients of Asian origin.

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Genetic Inheritance

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Autosomal recessive. Location of the Hageman factor gene was difficult; it was successively assigned to chromosome 6 and then 7, and now the gene map locus has been established as 5q33-ter.

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Pathophysiology

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FXII is a contact factor belonging to the kallikrein-kinin system or plasma. Patients affected with a deficiency in FXII do not experience abnormal bleeding because there is activation by other contact factors. The diagnosis is usually serendipitous. Partial thromboplastin time is elevated.

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Diagnosis

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Prolonged partial thromboplastin time; considerably decreased FXII assay. Condition usually discovered during routine laboratory examination.

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Clinical Aspects

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Elevated partial thromboplastin time, no clinical bleeding in normal conditions. Occasionally, mild blood loss has been reported, mainly following trauma or surgery. Severe liver disease may lead to reduced production of FXII, worsening the (biologic) condition. FXII deficiency was reported to be a risk factor for thromboembolism as a result of inactivation of fibrinolysis. The disorder may be a risk factor for early gestational losses.

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Precautions before Anesthesia

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Evaluate the coagulation profile and specific dosage of clotting factors. Even when partial thromboplastin time is considerably prolonged, there is no indication for fresh-frozen plasma, and common surgical procedures should not be contraindicated. These patients are not prone to develop a bleeding tendency but, on the contrary, might be at risk for thromboembolism (spontaneously and perioperatively).

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Anesthetic Considerations

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Classically, there are no specific contraindications to anesthesia. However, bleeding problems may arise in procedures requiring use of anticoagulants (cardiac surgery), requiring close followup of both global coagulation tests and individual dosages of clotting factors. Despite contradictory statements in the literature, these patients might be at increased risk for thromboembolism. Close monitoring of coagulation status and clinical and Doppler ultrasonography evaluation for suspected thromboembolism are highly recommended.

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Pharmacological Implications

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Administration of heparin may result in FXII deficiency; its use should be avoided in affected patients unless absolutely necessary (cardiac surgery, thromboembolism). Similarly, use of all anticoagulant agents is questionable and, basically, should be avoided.

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References

Hasegawa T, Uematsu M, Tsukube T, et al: Huge left ...

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