Thrombotic thrombocytopenic purpura

Alternative names

TTP

Definition

TTP is a blood disorder characterized by low platelets, low red blood cell count (caused by premature breakdown of the cells), abnormalities in kidney function, and neurological abnormalities. A similar clinical condition with overlapping features is hemolytic-uremic syndrome.

Causes, incidence, and risk factors

This disease is caused by a deficiency in the von Willebrand Factor cleaving protease, known as ADAMTS13. The loss of this enzyme results in large complexes of von Willbrand factor circulating in the blood, which in turn causes platelet clumping and red blood cell destruction.

Although most cases have no known cause, some cases may be related to a deficiency of ADAMTS13 at birth, cancer, chemotherapy, HIV infection, hormone replacement therapy and estrogens, and a number of medications in common use (including ticlopidine, clopidogrel, and cyclosporine A).

Symptoms

• Fever
  
• Weakness
  
• Easy fatigue
  
• Pallor
  
• Shortness of breath on exertion
  
• Heart rate over 100 per minute
  
• Purpura - purplish discolorations in the skin produced by small bleeding vessels near the surface of the skin
  
• Bleeding into the skin or mucus membranes
  
• headache
  
• Confusion
  
• Speech changes
  
• Alterations in consciousness
  
• Yellowish color to the skin (jaundice)
  

Signs and tests

• Platelet count is low
  
• CBC shows anemia
  
• Bilirubin is high
  
• Blood smear shows schistocytes and fragmented blood cells
  
• Urinalysis shows protein or microscopic blood particles
  
• Creatinine level is high
  
• Mucus membrane biopsy reveals platelet clots in small blood vessels
  

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 Blood is withdrawn from the patient as for a blood donation.