A SILENT BITE : FACTOR XII DEFICIENCY UNMASKED IN THE WAKE OF A SNAKE ENCOUNTER

Factor 12 or the Hageman factor plays an essential role in the initiation of the intrinsic or the contact pathway of coagulation. The activation of the pathway occurs either due to direct contact with a negatively charged surface like glass or kaolin or proteolytic activation through prekallikrein and kallikrein system. Activated partial thromboplastin time or aPTT clotting assay is the test which is used to evaluate the status of the intrinsic pathway. Factor 12 deciency is a rare genetic disorder which usually follows an autosomal recessive pattern of inheritance however an autosomal dominant inheritance has also been reported. There is no established data regarding the prevalence of Factor 12 deciency in the normal population. Based on a study conducted on 300 healthy blood donors, an estimated prevalence of 2.3% has been reported according to Halbmayer WM, et al. The incidence of the condition is about 1 in 1,000,000 individuals. In patients with a deciency of Factor 12, the aPTT is typically prolonged and there are no associated bleeding tendencies. More often there is an increased risk of arterial or venous thromboembolic events and the patient is usually asymptomatic according to Chaudhry LA, et al.