Clinical and hematologic features of thrombotic microangiopathies (TTP, HUS)

• TTP

  • Characterized by thrombocytopenia, microangiopathic hemolytic anemia, F, transient neurological defects, and renal failure

  • May be seen with a prodromal viral illness or HIV

  • Systemic formation of hyaline microthrombi (platelets and fibrin) in arterioles and capillaries with widespread organ dysfunction; activation of clotting proteins not important, and the PT and aPTT are usually normal

  • More common in women, incidence peaks in 4^th decade

  • Treatment with corticosteroids, platelet aggregation inhibitors, and intense plasmapheresis or exchange transfusion

  • Some people with this have an abnormally nonfunctioning, deficient, or Abs to vonWillebrand cleaving protease, which normally cleaves large vWF multimers to limit their platelet aggregating abilities

    • This is thought to be responsible for chronic, relapsing TTP

    • Cryoprecipitate-poor products should be used for plasmapheresis; these don’t contain the large vonWillebrand products, but do supply the cleaving proteases

• HUS

  • Like TTP, but without neurological c/s; the pathology is mainly in the kidneys

  • Most common in kids; associated with E. coli O157H7 or Streptococcus pneumoniae infection in kids, pregnant women, those with autoimmune d/o, and those who are immunosuppressed (including HIV)

  • Carries a better prognosis in kids than in adults (except with E. coli infection)

Category: Medical Subject Notes , Pathology Notes