Currently, the most effective treatment for TTP is therapeutic plasma exchange (TPE). Fresh frozen plasma (FFP), preferably cryoprecipitate-poor plasma (that lacks von Willebrand factor), is used as the replacement fluid in the treatment. The exchange takes place over several days until the patient's platelet count stabilizes above 100 x 109/L.
The logic of TPE is to rid the circulation of plasma containing ultra-large vonWillebrand factor (vWF) multimers. vWF is a large multimeric protein that is made by megakaryocytes and endothelial cells. It is is a key factor in platelet adhesion and also is responsible for carrying Factor VIII into the circulation. vWF binds glycoproteins Ib, IIb, and IIIa. The largest multimer is called ultra-large vWF and in normal plasma, it is cleaved into smaller fractions (necessary for balanced coagulation activity) by an enzyme processed by the gene, ADAMTS13. In patients with TTP, the enzyme activity is < 5% of normal and therefore, these ultra-large vWF molecules get into circulation, resulting in excessive platelet aggregation and microvascular thrombus formation.
Therapeutic plasma exchange has decreased TTP mortality rate from 90% to 15% since the treatment first came into use as the standard primary treatment of TTP in the 1970's. TPE does not cure TTP, but it arrests the manifestations of the disease until spontaneous remission occurs.