Factor VII verona coagulation disorder: double heterozygosis with an abnormal factor VII and heterozygous factor VII deficiency

A family with a peculiar defect of factor VII is described. The propositi, a brother and sister, were born of a nonconsanguineous marriage and presented a mild to moderate bleeding tendency since childhood (epistaxis, excessive bleeding after tooth extraction). The coagulation pattern was characterized by a mildly prolonged prothrombin time, normal partial thromboplastin time, and normal Stypven-cephalin clotting time. Prothrombin consumption and thromboplastin generation were normal. Factor VII activity was 20%-25% of normal but factor VII antigen was about 50% of normal. The father and other members of his family had factor VII activity of 36%-50% of normal but the factor VII antigen level was 100%. The mother had factor VII activity and antigen levels of about 50% of normal. It appeared that the propositi had inherited an abnormal factor VII from the father and a heterozygous factor VII deficiency from the mother. Therefore, the defect would seem to result from a double heterozygous state. The brother of the propositi had 65% factor VII activity and a normal factor VII antigen, probably the result of the interaction of a paternal abnormal factor VII gene and a normal maternal gene. The condition is referred to as factor VII Verona.