[A case of familial antithrombin III variant complicated by recurrent pulmonary infarction].

We present a 36-year-old male who developed pulmonary infarction secondary to antithrombin III variant. He was admitted to our hospital with progressive chest pain and hemosputum. The presence of multiple defects on 99mTc perfusion scan indicated the diagnosis of pulmonary infarction. He had a past history of pulmonary infarction 4 years before this episode as well as a family history of recurrent thromboembolic disease. Through coagulation studies revealed that the concentration of antithrombin III antigen and progressive antithrombin activity were within normal limits, while heparin cofactor activity was decreased markedly. Of 5 people in his family, 4 proved to have low heparin cofactor activity. These data suggest that functional abnormality of antithrombin III seems to be closely associated with pulmonary infarction.