Summary

Immune-mediated heparin-induced thrombocytopenia (HIT) isa rare but severe adverse effect of heparin therapy. Onlyfew data are available on clinical presentation, diagnosis andmanagement of HIT in children. Records of all patients sent toour laboratory between 1995 and November 2003 werereviewed. To identify literature reports a Medline search wasperformed, the reference lists of those publications werescreened and the abstracts of meetings on thrombosis andhemostasis between 2000 and 2003 were assessed. We identified12 new HIT patients between 13 months and 18 years ofage from our laboratory and 71 reports on HIT in children inthe literature. For the assessment of frequency of HIT allstudies enrolling > 100 patients were analyzed. HIT is rare in children. In pediatric patients, there seem to be two risk groups:newborns and infants under 4 years of age undergoing cardiacsurgery (incidence ~ 1-2%), and teenagers treated with heparinfor thrombosis. For confirmation of HIT in children, antigenassays are most important. There are conflicting data on theoptimal cut-off, with one randomized, double-blind trial indicatingthat the cut-off established in adults is appropriate.There are no systematic studies on alternative anticoagulants inchildren affected by HIT. Most data are available for lepirudinand danaparoid. Substitution of unfractionated heparin bylow-molecular-weight heparins for regular anticoagulation mayreduce the incidence of HIT.