Case Report Cerebral Infarction in a Heterozygote With Variant Antithrombin III

Background: We report a heterozygous case of familial qualitative deficiency of antithrombin III associated with cerebral infarction. Case Description: A 33-year-old man had a history of recurrent transient ischemic attacks from the age of 28. Cerebral computed tomography at age 29 disclosed a low-density area in the left frontal lobe, and an internal carotid angiogram showed branch occlusion of the right anterior cerebral artery and stenosis of the left middle cerebral artery. Occlusion of the right middle cerebral artery developed thereafter. The plasma antithrombin III antigen concentration and progressive antithrombin activity were normal, but plasma heparin cofactor activity was low in the patient and his father. Nucleotide sequence analysis of the proband's deoxyribonucleic acid showed no mutation in exons II and VI of antithrombin III. Conclusions: We conclude that abnormal antithrombin HI with defective heparin binding, even though heterozygous, may cause ischemic stroke in young adults. We named this antithrombin III variant "Antithrombin III Nagasaki." (Stroke 1992;23:1822-1825)