Case studies in heparin-induced thrombocytopenia.

Type II heparin-induced thrombocytopenia (HIT) is an immunological disorder characterized by antibodies to heparin-platelet factor 4 complexes and a high risk of thrombotic complications. Here, we present illustrative case histories to educate the reader on evaluation and management of this complex syndrome. Cases include typical and unusual presentations of the syndrome, and commonly encountered problems and pitfalls of therapy. Major points illustrated are, (1) occurrence of HIT with any dose or form of heparin; (2) misperceptions on the diagnostic criteria; (3) correct (thrombin inhibitors) and incorrect (platelet transfusions and warfarin) management; (4) influence of management strategy on clinical outcomes; (5) severity of the syndrome; and (6) potential for both anamnestic response to heparin and disappearance of HIT antibodies over time. Effective therapy of HIT involves both the prompt recognition of the syndrome and its proper management.