The white clot syndrome or heparin associated thrombocytopenia and thrombosis (WCS or HATT) (26 cases).

The Authors report a new iatrogenic complication of preventive or curative standard heparinotherapy. This so called "white clot syndrome" or "Heparin associated thrombocytopenia and thrombosis" is an anatomico-clinical entity characterized by severe, multiple, recurrent, arterial and/or venous thromboembolic accidents which are sometimes fatal. They appear, paradoxically, under heparin treatment and are concomitant with thrombocytopenia (generally less than 100 10(9)/l). Antiplatelet immunoallergic phenomena, via type IgG antibodies, induced by heparin, are the most commonly admitted in physiopathology; however they remain controversial. Treatment of "WCS" includes urgent suppression of standard heparin, administration of antivitamin K, or the new generation of low molecular weight heparin. This series presents 26 cases of HATT treated by LMWH (CY 216 CHOAY). Severe complications must be surgically cured. Prevention of WCS or HATT is mandatory by the systematic survey of platelet count during heparinotherapy.