Combined Severe Factor XI Deficiency and von Willebrand’s Disease

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Abstract
A family whose members demonstrated deficiency of factor XI and also showed mild von Willebrand’s disease is discussed. Two siblings had this combined defect, and a third was only affected with mild depression of factor VIII coagulant activity. Their mother showed laboratory findings of mild von Willebrand's disease and had reduced factor XI antigen, whereas their father was normal. Cross immunoelectrophoresis of the factor VIII antigen showed abnormal mobility when plasmas of the four affected members (three siblings and mother) were tested and compared with normal plasmas and the father’s plasma. The in-vitro effects of normal plasma, hemophilic plasma, highly purified factor XI, and cryoprecipitate were evaluated. Normal plasma completely corrected the abnormal activated partial thromboplastin time (APTT), whereas partial corrections were seen when hemophilic plasma was added to the plasma of the factor XI-deficient patients. Highly purified unactivated factor XI also showed partial corrective effects on the APTT. Cryoprecipitate containing 5 U/ml of factor VIII and 1.6 U/ml of factor XI corrected the APTT to normal when mixed in equal amounts with the patients’ plasma. Cryoprecipitate and frozen plasma were also tested in one of the affected siblings before knee surgery. The contents of ten bags of cryoprecipitate infused intravenously partially corrected the APTT for over 72 hours; factor VIII coagulant showed a prolonged half-life survival (~72 hours), whereas factor VIH-related antigen had a shorter survival (24 hours). During surgery the patient was infused with frozen plasma because of the higher concentrations of factor XI; on this preparation her factor XI coagulant fluctuated between 40% and 60% during this period. Histocompatibility studies done for all the family members disclosed that the inheritance of these two factor deficiencies was independent of the HLA system.