[Are we to pay attention to factor XII deficiency?].

UNLABELLED: Severe coagulation factor XII (FXII) deficiency is a very rare, mysterious and not well known inherited condition. Unlike other coagulation factor deficiencies, it is totally asymptomatic. Surprisingly, it does not lead to abnormal bleeding, even with major surgical procedures. The explanation for the lack of bleeding manifestations is unknown. It is suggested, but unproven, that patients are not sufficiently protected from thrombosis. FXII deficiency is usually discovered by accident through a routine coagulation testing done prior to surgery. Since FXII plays an important role in clot formation during in vitro measurements, its deficiency causes a marked prolongation of the activated partial thromboplastin time in the laboratory examination. The main concern related to FXII deficiency is the unnecessary testing, delay in health care and worry of surgical interventions that may be prompted by the abnormal laboratory result.

KEY WORDS: activated partial thromboplastin time - bleeding - blood coagulation - factor XII.