The symptoms of thrombotic thrombocytopenic purpura (TTP) are caused by tissue damage. They are accompanied by low platelet counts, as the platelets are used up in forming clots.

The main symptoms are:

• Neurological disturbances, including headache, fits, confusion, reduced consciousness and stroke.
• Bleeding from small vessels under the skin (purpura).
• Jaundice: yellowing of the skin and the whites of the eyes.
• Fever.

Diagnosis of TTP is based on these symptoms along with the following signs in blood samples:

• Low platelet count.
• Low red blood cell count (anaemia), with fragments of red blood cells visible under the microscope.
• High levels of immature red blood cells (reticulocytes).
• No evidence of autoimmune disease in the Coombs test.
• Normal blood clotting.
• High levels of lactate dehydrogenase, bilirubin, urea or creatinine (markers of tissue damage).

The presence of blood or protein in the urine is a further symptom of TTP.

Low activity levels of ADAMTS13 can also be used to diagnose TTP, but this is currently only used as a research tool.