Thrombotic thrombocytopenic purpura following stem cell transplantation.

Thrombotic thrombocytopenic purpura (TTP) occurring after stem cell transplantation is poorly understood. The literature is scant and heterogeneous; little is known about the condition's pathogenesis except that it appears to differ from that of classical or de novo TTP. There are no widely agreed diagnostic criteria hence, it is difficult to compare the major findings of the relatively small, single centre series that have been reported. The true incidence is disputed and risk factors have only recently been evaluated. Plasma exchange is commonly employed for the therapy of severe post-transplant TTP but there are no data that support its use. This review summarises the state of knowledge of post-transplant TTP in 2002, addressing all the aforementioned issues and aims to provide the basis for further systematic study of this problematic complication of transplant.