Porpora trombotica trombocitopenica (PTT) o sindrome di Moschowitz: una vera urgenza ematologica

Abstract

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy caused by congenital or inherited disorders involving the processing of the ultra-large forms of von Willebrand factor. As a result, platelet-rich microthrombi form in the small arterial vessels of various organs, particularly those of the brain, heart, and kidneys. The idiopathic autoimmune form of TTP is the most common. There are various subgroups of acquired TTP associated with HIV infection, sepsis, pregnancy, autoimmune disease, various disseminated malignancies, and drugs. If not promptly treated, TTP is associated with high mortality, making it a true medical emergency. The article is based on a review of the literature published between January and October of 2009. Its aim is to clarify the diagnosis, treatment, and follow-up of TTP. Diagnostic criteria include the presence of microangiopathic hemolytic anemia associated with thrombocytopenia in the absence of other obvious causes. Assays of ADAMTS13 activity and titration of acquired antibodies against this enzyme are indicated in the follow-up of disease and as prognostic indicators. Treatment centers around daily plasma exchange associated with immunosuppressant drug therapy, particularly steroids and more recently the monoclonal anti-CD20 antibody rituximab. Despite improved treatment, TTP is still associated with significant mortality (10–20%), particularly when plasma exchange is initiated late. Relapse also occurs in a substantial proportion of patients (10–40%) although the frequency of this outcome may be reduced by rituximab therapy.