In this study, we retrospectively analysed the clinical features, risk factors and outcome of 22 patients with
thrombotic thrombocytopenic purpura (
TTP) occurring after allogeneic
stem cell transplantation. All but two of these patients received stem cells from unrelated donors (UDs), two-thirds were female, three-quarters were adults and leukaemia was the major reason for transplant. The incidence of
TTP was 20 out of 332 patients (6%) with UD transplants and two out of 104 recipients (2%) of matched sibling allografts (P = 0.16). In order to ascertain basic demographic risk factors for the development of
TTP, we compared the 22 patients with 434 patients who did not develop
TTP. Compared with patients who did not develop
TTP, patients with
TTP were nearly three times older (P < 0.001) and were more than twice as likely to be female (P = 0.001). Because > 90% of patients were recipients of UD marrow, we then compared the 20 UD-
bone marrow transplantation (BMT) patients with 60 randomly selected UD-BMT patients who did not develop
TTP. On univariate analysis, age and female gender were again significant risk factors, as was grade II-IV acute
graft-versus-host disease (GvHD) (P = 0.002), and there was a trend towards an association with chronic GvHD (P = 0.083). However, after logistic regression analysis, only age and sex remained significant (P < 0.001 and 0.009 respectively). We report an 86% mortality with only three survivors out of 22 patients, and one of these remains thrombocytopenic and red cell transfusion dependent, possibly in part because of graft hypoplasia. Six out of 17 patients responded to
plasmapheresis, but the majority of them ultimately succumbed because of
TTP, often in association with GvHD or
fungal infection.