A new family with congenital factor XII deficiency

The case of a patient with Hageman trait and his family study are reported. Commercial plasma thromboplastin time (PTT) reagents showed a good sensitivity for detecting the plasma defect. By prolonging the incubation time of the mixture containing PTT reagent and factor XII-deficient plasma the abnormal coagulation times were not corrected. Thus, a concomitant Fletcher factor deficiency could be excluded.