The Malmo model for immune tolerance induction: impact of previous treatment on outcome

Ten patients, who had been treated according to the Malmo model for immune tolerance induction (ITI), were analysed regarding treatment with clotting factors and chemotherapy during the time period between inhibitor detection and ITI. Of the patients who were successfully rendered tolerant (n = 6) all but one had received treatment with FVIII, either alone (n = 1), or combined with cyclophosphamide (n = 4). Of the patients who did not become tolerant, three of four had received treatment with FVIII during the inhibitor period but only one with FVIII and chemotherapy. The total amount of treatment received was in general much lower in the group that did not become tolerant. In individual cases, it appeared very clear that the inhibitor level and anamnestic response was substantially reduced prior to the ITI using the Malmo treatment model. We conclude that treatment of acute bleeds during the inhibitor period may be of importance for ITI and that the different response rates published for different immune tolerance regimens most likely do not reflect the true response rate for the respective regimen.