Summary
Hereditary factor XII deficiency is reported in 2 unrelated Norwegian families.
Case 1 was a 50 year old female, who was investigated because of a subcutaneous hematoma
of unexplained cause. She had bruised easily, but neither she nor members of her family
had suffered from definite and marked bleeding tendency. In the last years she had
had hemoptyses of unknown cause. Five years ago she had a slight cerebral vascular
episode with temporary hemiparesis in extremities. A sister had died 46 year old in
cerebral apoplexy. The parents were first cousins.
Case 2 was a 72 year old male. He had no definite history of bleeding tendency, neither
had members of his family. He suffered from diabetes, hypertension and vascular encephalopathy.
After the age of 67 he had several attacks of cerebral apoplexy with paresis of extremities,
ataxia and parkinsonism.
Blood factor XII was for both case 1 and case 2 found lower than 1% of normal average,
while other coagulation factors were in the main normal. A probable partial factor
XII deficiency was demonstrated in some of the relatives of case 1 and case 2, consistent
with the hypothesis that the principal patients were homozygous for their coagulation
abnormality.
The study lends some support to a hypothesis that a factor XII defect might contribute
to a hemostatic disorder, and especially to an increased risk for cerebral apoplexy.
