Inhibitor treatment in haemophilias A and B: summary statement for the 2006 international consensus conference E. BERNTORP,* A. SHAPIRO,  J. ASTERMARK,* V. S. BLANCHETTE, à P. W. COLLINS,§ D. DIMICHELE, – C. ESCURIOLA,** C. R. M. HAY,   W. K. HOOTS, àà C. A. LEISSINGER,§§ C. NEGRIER, –– J. OLDENBURG,*** K. PEERLINCK,    M. T. REDING ààà and C. HART§§§ *Department of Coagulation Disorders, Malmo ¨ University Hospital, Malmo ¨ , Sweden;  Indiana Hemophilia and Thrombosis Center Inc., Indianapolis, IN, USA; àDivision of Haematology/Oncology, The Hospital for Sick Children, Toronto, ON, Canada; §Arthur Bloom Haemophilia Centre, University Hospital of Wales, Cardiff, UK; –Weill Medical College of Cornell University, New York, NY, USA; **Centre of Pediatrics III, Johann Wolfgang Goethe University Hospital, Frankfurt am Main, Germany;   University Department of Haematology, Manchester Royal Infirmary, Manchester, UK; ààGulf States Hemophilia and Thrombophilia Center, The University of Texas Health Science Center, Houston, TX, USA; §§Tulane University School of Medicine, New Orleans, LA, USA; ––Haemophilia Treatment Center, Hospital Edouard Herriot, University of Lyon, Lyon, France; ***Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany;    Haemophilia Treatment Center, University Hospitals Leuven, Leuven, Belgium; àààFairview-University Medical Center, University of Minnesota, Minneapolis, MN, USA; and §§§InforMEDical Inc., Narberth, PA, USA Summary. Participants in an international confer- ence on the management of haemophilia patients with inhibitors developed a jointly authored sum- mary of the findings and conclusions of the confer- ence. Current knowledge of the genetic and immunologic mechanisms underlying inhibitor devel- opment was briefly summarized. Concerning the purported treatment-related risk factors, conference participants commented on the limitations of the available evidence and the need for more rigorous prospective research in a fully genotyped population. Other clinical considerations discussed included the unproved utility of routine surveillance, the need for assay standardization, the management of acute bleeding and approaches to joint disease prophylaxis and immune tolerance induction (ITI). A number of issues were identified as needing further investigation in larger prospective studies, ideally through inter- national cooperation. Such studies should enrol cohorts that have been scrupulously defined in terms of mutation status and treatment exposure. Finally, conference participants urged their colleagues to participate in the currently ongoing international trials of ITI. Keywords: diagnosis, guidelines, haemophilia, inhib- itors, treatment Introduction The International Consensus Conference on Inhib- itor Treatment in Hemophilia A and B, held in Cambridge, Massachusetts, 24–25 March 2006, was convened with the goal of formulating recommen- dations on the management of the patient with inhibitors to factor VIII (FVIII) or factor IX (FIX) where sufficient evidence exists to guide clinical practice, and of identifying priorities for research where the data are inadequate. The conference format combined brief presentations with extended periods of open discussion. The conclusions reached over the course of the 2-day conference are summar- ized briefly below and presented at greater length in the individual papers and accompanying discussions that constitute the conference proceedings. The development of inhibitors is today the most serious complication of haemophilia and its treat- ment. Inhibitors occur in 20–30% of patients with haemophilia A but in only 5% of patients with hae- mophilia B. In haemophilia B, however, inhibitors Correspondence: Erik Berntorp, Department of Coagulation Dis- orders, Malmo ¨ University Hospital, SE-205 02 Malmo ¨ , Sweden. Tel.: +46 40 332392; fax: +46 40 336255; e-mail: erik.berntorp@medforsk.mas.lu.se Accepted after revision 4 September 2006 Haemophilia (2006), 12 (Suppl. 6), 1–7 Ó 2006 Blackwell Publishing Ltd 1