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Pathomorphological aspects of heparin-induced thrombocytopenia II (HIT-II syndrome)

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 The therapeutic use of heparin results in thrombocytopenia in 5–30% of patients. In 0.1–1% of patients treated with heparin, the platelet count decreases to between 100 × 109/l and 50 × 109/l and leads to severe synchronous central arterial and venous thrombosis with a mortality of 18–36%. This is known as ”white-clot syndrome” or heparin-induced thrombocytopenia II (HIT-II syndrome). Whilst the clinical aspects and the central type of thrombosis in HIT-II syndrome are well documented, the histomorphology and differential diagnosis of thrombosis are not. We report three cases of HIT-II syndrome with thrombosis of the central arteries and veins. The HIT-II thrombi could be differentiated from thrombi of other origins, particularly from mural thrombi. Heparin-induced thrombi were seen on microscopical examination to be like onion skin in structure, and immunohistochemistry showed that they had a markedly reduced content of fibrin and clearly enhanced amounts of IgG and IgM. The layered structure thus implied appositional growth. The thrombi in HIT-II syndrome do not seem to be induced by activation of the coagulation cascade, but by platelet aggregation mediated by anti-platelet antibodies.

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Received: 12 September 1997 / Accepted: 6 January 1998

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Hermanns, B., Janssens, U., Handt, S. et al. Pathomorphological aspects of heparin-induced thrombocytopenia II (HIT-II syndrome). Virchows Archiv 432, 541–546 (1998). https://doi.org/10.1007/s004280050203

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  • Key words Heparin
  • Thrombocytopenia
  • Thrombosis
  • Pathomorphology
  • Immunohistochemistry