THROMBOTIC THROMBOCYTOPENIC PURPURA (TTP)

• Pathological Basis:
  • The pathogenesis of TTP remains a subject of controversy. It has been suggested that the thrombi in this disorder derive exclusively from platelets and that the fibrin is derived from platelet fibrinogen.
  • Current belief is that the endothelial cells are the site of the initial injury in this disorder. The type of injury may be immunologic, either cell-mediated or IgG-mediated. Following are the mechanisms proposed for pathogenesis of TTP:
    • Platelet aggregation factor.
    • Decreased production of prostagladins I2.
    • Decreased production of plasminogen activator by endothelial cells.
    • Presence of large von Willebrand factor multimers in plasma (may reflect abnormal endothelial processing of von Willebrand factor).
• Treatment:
  • Plasma pheresis.
  • Infusion of prostacyclin may be helpful.