Thrombotic Thrombocytopenic Purpura

Question 1

Define TTP

Answer 1

Rare blood disorder characterised by thrombosis of small vessels
Pentad of microangiopathic haemolytic anaemia, acute renal failure,
thrombocytopenia, fever and neurologic symptoms

Question 2

What are the causes/risk factors of TTP?

Answer 2

Unknown aetiology
Unusually large vWF multimers and a lack of ADAMTS13 (vWF
cleaving enzyme) -> vWF interacts with platelet membranes -> platelet aggregation ->
thrombosis in microvasculature
• Idiopathic (?autoimmune)
• Congenital (Upshaw-Schülman syndrome)
• Cancer
• Bone marrow transplant
• Pregnancy
• Drugs e.g. quinine

Question 3

What are the symptoms of TTP?

Answer 3

• Malaise
• Fever

Neurological symptoms
• Headache
• Confusion
• Focal abnormalities e.g. hemiplegia, paraesthesia, visual disturbances, aphasia
• Seizures
• Coma

Question 4

What are the signs of TTP?

Answer 4

Thrombocytopenia
• Purpura
• Petechiae
• Ecchymoses

Question 5

What investigations are carried out for TTP?

Answer 5

• FBC - normocytic Anaemia (Low Hb).
- High MCHC due to the presence of reticulocytosis and schistocytosis.
- Thrombocytopaenia
• Blood Smear - schistocytes indicate microangiopathic process from physical destruction within the vasculature, indicative of MAHA.
• BR - elevated Unconjugated BR, due to increased haemolysis.
• LDH - elevated
• Clotting - normal PT, APTT and Fibrinogen.
• Haptoglobin - low; Haptoglobin binds free Hb, with low plasma values suggestive of increased free Hb.
- High LDH and Low Haptoglobin is a useful marker of haemolysis.
• Urinalysis - dipstick positive for blood, negative for RBC. Haemoglobinuria is present in intravascular haemolysis.
• Coombs’ Test - for haemolytic anaemia. The test is used to detect IgG or complement bound to the red cell surface. Positive suggests immune aetiology; negative suggests non-immune aetiology.