Summary
In some members of 4 Norwegian families, a slight to moderate bleeding tendency was
found to be associated with a partial blood factor XII defect, the factor activity
about half of average normal level. In keeping with the low factor XII, surface activation
rate of factor VII in plasma was found significantly decreased.
The disorder seems to be transmitted as an autosomal intermediately dominant trait.
A high incidence of cerebral apoplexy was recorded in the patients, and the first
cerebrovascular attack had in most affected patients occurred at a relatively early
age.
In some of the patients attacks of localized edema, severe headache and abdominal
pain, and different types of allergy remind of the problems of the demonstrated non-coagulation
properties of factor XII.
The results are discussed.
