Spontaneous heparin-induced thrombocytopenia syndrome: 2 new cases and a proposal for defining this disorder

Theodore E. Warkentin*, Paul A. Basciano, Jared Knopman, Richard A. Bernstein

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

110 Scopus citations


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 2 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-platelet factor 4 (PF4)/heparin immunoglobulin (Ig)Gin 2 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 (ie, where heparin use precedes HIT but is not required for subsequent development or worsening 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.

Original languageEnglish (US)
Pages (from-to)3651-3654
Number of pages4
Issue number23
StatePublished - Jun 5 2014

ASJC Scopus subject areas

  • Hematology
  • Biochemistry
  • Cell Biology
  • Immunology


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