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.

Successful treatment of congenital thrombotic thrombocytopenic purpura using the intermediate purity factor VIII concentrate BPL 8Y.

There is increasing evidence that congenital thrombotic thrombocytopenic purpura (TTP) is caused by an absolute deficiency of von Willebrand factor-cleaving protease. The recent identification of this protease and the development of assays for its detection have enabled its quantification in a number of plasma products, including some commercial intermediate-purity plasma-derived factor VIII preparations. We report the successful, weekly prophylactic use of a commercial intermediate-purity plasma-derived factor VIII concentrate in the treatment of a 14-year-old girl with severe congenital TTP who had previously required transfusions of fresh-frozen plasma every 2 weeks from the age of 4 months.

Severe prekallikrein deficiency associated with homozygosity for an Arg94Stop nonsense mutation.

An elderly patient with no abnormal bleeding presented with prolongation of the activated partial thromboplastin time (aPTT). Preincubation of plasma with aPTT reagent caused shortening of the abnormal clotting time. Plasma prekallikrein (PK) activity and antigen were <5 u/dL. Molecular analysis showed a homozygous Arg94Stop substitution in the PK gene, predicted to prevent expression of the mutant allele. The five heterozygous offspring of the proband each showed a normal aPTT but reduced PK activity and antigen. This is the first description of a kindred in which absence of expression of one or both PK alleles has been confirmed by genotype.