[Coagulation factor XII deficiency, a contribution to thrombophilia].

The hereditary deficiency of Hageman's factor rarely occurs. The patients are mostly detected by chance. The leading symptom is the considerably prolonged partial thromboplastin time. A haemorrhagic diathesis is not present. Since in these patients thromboemoblic diseases are possible, in an ascertained diagnosis the prevention of thrombosis should be performed.