(Can also be known as Hageman factor deficiency)
This somewhat mysterious deficiency was first discovered in 1955 and named after John Hageman, the first patient diagnosed with the condition. The incidence of Factor XII deficiency is estimated at 1 in 1 million. This deficiency is inherited in an autosomal recessive fashion, which means it affects men and women equally. It has been reported that factor XII levels seem to be lower among Asians, than any other ethnic group.
The mystery of Factor XII centers on how the protein is a step in the process of forming a clot, but people with the deficiency usually do not experience bleeds and normally do not require treatment. Having a low factor XII level has little to no clinical significance.
Even with major surgery, bleeding manifestations are extremely rare. In fact, most people only get diagnosed by chance, or during pre-screening blood tests for surgery. Since bleeding time is usually normal, diagnosis is made by a prolonged activated partial thromboplastin time (aPTT) test. A specific factor XII assay is necessary to confirm the initial diagnosis.
Treatment is usually unnecessary. There is some indication that Factor XII deficiency may predispose people to thrombosis, but this has not been clearly established