Thrombotic Thrombocytopenic Purpura
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- Thrombotic thrombocytopenic purpura (TTP) is a severe disorder of abnormal clotting affecting multiple organ systems.
- Classically characterized by pentad of:
- Hemolytic anemia
- Mild renal dysfunction
- Neurologic signs
- Uncommon to see all 5 features in 1 patient; if present, severe end-organ damage or ischemia has likely taken place.
- Thrombocytopenia and hemolytic anemia are the most common features.
- Associated with acquired or congenital deficiency of plasma von Willebrand factor–cleaving protease (VWFcp)
- Patients who present with severe neurologic abnormalities with acute renal failure are best described by the comprehensive term TTP-HUS
- Acute onset
- Fulminant course lasting days to a few months
- Nearly always fatal without treatment:
- >90% mortality without treatment
- Reverses to >90% survival with modern treatment
- Clinical presentations include:
- Familial, chronic, or relapsing
- Drug induced:
- Allergic or immune mediated (quinine, ticlopidine, clopidogrel)
- Dose-related toxicity (mitomycin C, cyclosporine)
- Pregnancy, postpartum associated:
- 10–25% of cases
- Bone marrow transplantation associated
- More common in the 3rd–6th decades of life
- Uncommon in pediatric or geriatric populations
- Women affected about twice as frequently as men
- Unknown primary stimulant; possibly systemic endothelial cell damage results inactivation of coagulation pathway
- Platelet aggregation and fibrin deposition occurring in arterioles and capillaries leading to microthrombi and obstruction to blood flow
- Platelet aggregation leads to:
- Consumption of platelets
- Widespread microvascular hyaline thrombotic lesions
- Microvasculature obstruction with platelet aggregates leads to:
- Red cell hemolysis
- Accumulation of heme breakdown products
- End-organ ischemia results from diffuse thrombosis in small vessels:
- Most common in heart, brain, kidney, pancreas, and adrenal glands
- Deficiency of vWFcp causes failure of control of coagulation pathway.
- Some cases are genetic/familial.
- VWFcp was recently identified as new member of ADAMTS family and designated ADAMTS13.
- Mutations in ADAMTS13 gene cause autosomal recessive form of chronic relapsing TTP.