Congenital factor VII deficiency. Clinical and laboratory characteristics of a newly discovered kindred

Four generations of a newly discovered kindred suffering from congenital factor VII deficiency have been studied. The abnormality was transmitted as an autosomal recessive character and resulted in homozygotes with less than 1% factor VII procoagulant activity. Antibody neutralization tests using a monospecific rabbit anti-human factor VII antibody demonstrated the presence of factor VII antigen in excess of factor VII procoagulant activity. The disorder has therefore resulted from the presence of a functionally abnormal factor VII molecule and not from a true deficiency of this factor. When the plasmas from the homozygotes were tested in the prothrombin time test using human, rabbit and ox tissue thromboplastins, a progressive diminution in the ability of these reagents to detect the factor VII procoagulant deficiency was observed. These differences were however small and the complete insensitivity of ox brain thromboplastins that characterizes the factor VII Padua abnormality was not observed.