RESUMO
A 59-year-old female was admitted with left flank pain. She had heat intolerance and dyspnea for the last 3 years. She was diagnosed as having renal and splenic infarction. 2 phase computed tomography (CT) scan on abdomen and pelvis showed a non-enhancing portion at the anterior aspect of the left kidney and multifocal low density at the spleen. Laboratory examinations revealed TSH 0.0004 uIU/mL, Free T4 2.69 ng/dL, T3 1.67 ng/mL, anti TPO antibody 207 U/mL (positive), anti TG antibody 52.7 U/mL (positive) and TSH receptor antibody >40 U/mL. A diagnosis of hyperthyroidism was made. Factor VIII activity increased over 160% (normal range 60-140), which has been known to increase in the cases of hyperthyroidism. Except for an increased factor VIII activity there were no thrombogenic abnormalities. She recovered well after the treatment with methimazole in addition to warfarin followed by intravenous heparin. This case is consistent with the assumption that hyperthyroidism, probably through a factor VIII-mediated hypercoagulability, may be a predisposing factor for the development of renal and splenic infarction.