The clinical features, risk factors and outcome of thrombotic thrombocytopenic purpura occurring after bone marrow transplantation

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 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