SINUS THROMBOSIS CAUSED BY HEPARIN-ASSOCI ATED THROMBOCYTOPENIA

Using MRI angiography, sinus thrombosis was diagnosed in a 42-year old female patient who had been treated with intravenous heparin for 18 d ays because of a symptomatic stenosis of the internal carotid artery. Moreover, thrombosis was also found in both the common carotid artery and external carotid artery, and the platelet count dropped from 526/n l to 111/nl. Once heparin application was stopped, giving warfarin for anticoagulation instead, platelet levels quickly returned to normal v alues. Symptoms, blood findings and clinical course suggested the diag nosis of heparin-induced thrombocytopenia with thrombus formation (HAT type II) in this patient, which could be confirmed by specific labora tory tests. in HAT type II, heparin-dependent IgG-antibodies against p latelets and endothelial cells are formed, causing intravasal aggregat ion of platelets with subsequent blood clotting in both arteries and v eins. Given an incidence of 0.5-5%, these immunologically caused throm bocytopenias are among the rare side effects of heparin therapy.