Thrombotic Thrombocytopenic Purpura

Classically, thrombotic thrombocytopenic purpura (TTP) is diagnosed when at least four of the following five elements are present, in the absence of another explanation: microangiopathic hemolytic anemia (MAHA), thrombocytopenia, decreased renal function, fever, and neurologic abnormalities. The cause of this disease process is uncertain, but it is characterized by microthrombi (deposits composed of platelets and fibrin) within the lumina of capillaries and arterioles in various locations, creating a variable clinical presentation.

Causes

Although the exact causes TTP is unknown, experts believe that an abnormal, inflammatory reaction within the blood stimulates the deposition of platelet-rich thrombi. It has been observed that a circulating and/or missing factor in the blood perpetuates the process. Therefore, TTP patients often benefit from treatment that removes the plasma (fluid, non-cellular part of the blood) and replaces it with donor plasma.

Symptoms

• Neurologic abnormalities are seen most commonly (headache, confusion, cranial nerve palsies, hemiparesis, or coma).
• Other symptoms (dependent on organ system involved)
• See Thrombocytopenia

Treatment

Plasmapheresis, or plasma exchange, is used to remove unwanted substances from the blood (large von Willebran protein complexes), and to replace the missing protease. Blood is withdrawn from the patient as for a blood donation.

Then the plasma portion of the blood is passed through a cell separator. The remaining portion of the blood is saved, reconstituted with fresh plasma, and returned to the patient as a blood transfusion.

In thrombotic thrombocytopenic purpura, this treatment is repeated daily until blood tests show improvement. People who do not respond to this treatment, or have frequent recurrences, may require the removal of the spleen, corticosteroids, or other immune suppression.