Inherited heterozygous protein C deficiency and dysfunctional protein S with recurrent venous thrombotic diseases: a study of three generations of a Japanese family.

We describe a rare occurrence of a family affected with venous thrombosis, exhibiting a protein C (PC) deficiency and dysfunctional protein S (PS). The propositus and his father developed recurrent venous-thrombosis. Their PC deficiency was characterized by low levels of both antigen and activity, and their dysfunctional PS was suggested by low PS activities despite the presence of normal free PS antigen. Over three generations, six family members had a PC deficiency, and three had both a PC deficiency and a dysfunctional PS. The mode of inheritance of PC deficiency appears to be autosomal dominant.