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Spontaneous heparin-induced thrombocytopenia syndrome: two new cases and a proposal for defining this disorder.
Blood. 2014 Mar 27;
Authors: Warkentin TE, Basciano PA, Knopman J, Bernstein RA
Abstract
The existence of "spontaneous" heparin-induced thrombocytopenia (HIT) syndrome (or "autoimmune HIT"), defined as a transient prothrombotic thrombocytopenic disorder without proximate heparin exposure serologically indistinguishable from HIT, is controversial. We describe two new cases presenting with thrombotic stroke/thrombocytopenia, one following shoulder hemi-arthroplasty (performed without heparin), and the other presenting to the emergency room without prior hospitalization, heparin exposure or preceding infection. Both patients tested strongly positive for anti-PF4/heparin IgG in two different immunoassays, and in the platelet serotonin-release assay. Crucially, both patients' sera also caused strong (>80%) serotonin-release in the absence of heparin, a serologic feature characteristic of "delayed-onset" HIT (i.e., where heparin use precedes HIT but is not required for subsequent development of thrombocytopenia). We propose that a rigorous definition of spontaneous HIT syndrome should include otherwise unexplained thrombocytopenia/thrombosis without proximate heparin exposure, and with anti-PF4/heparin IgG antibodies that cause strong in-vitro platelet activation even in the absence of heparin.
PMID: 24677540 [PubMed - as supplied by publisher]