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Hemolytic Uremic Syndrome

HUS is characterized by (AIIMS May 10)
  1. Microangiopathic haemolytic anaemia (MAHA): (isntravascular haemolysis + red cell fragmentation).
  2. ARF
  3. Thrombocytopenia
  4. Fever

Extra Edge


CNS involvement is not a feature of HUS.

  1. Cause 90% due to E coli 0157 (LQ 2012): produces a verotoxin which attacks endothelial cells.
  2. This affects young children most, often occurring in outbreaks due to consumption of undercooked contaminated meat, with abdominal pain, bloody diarrhea and ARF.


  1. Endothelial damage triggers thrombosis, platelet consumption and fibrin deposition, mainly in the renal microvasculature.
  2. The strands cause mechanical destruction of passing red blood cells.
  3. Thrombocytopenia and ARF occur.
Blood film: fragmented RBC platelets, HB is reduced but Clotting tests are normal. There may be haematuria, proteinuria. Often resolves spontaneously. 


Extra Edge

  1. Fibrinogen level, and assays for fibrin degradation products such as "D-Dimers", are generally normal despite the low platelet count (thrombocytopenia)
  2. Coombs test is negative.

Treatment: No specific treatment, dialysis for ARF

Prognosis: Worse in non- E. Coli cases. Mortality 3-5%.

Thrombotic thrombocytopenic purpura (TTP) (AIIMS Nov 10)

It is a pentad of:
  1. Fever
  2. Fluctuating CNS signs (eg fits, hemiparesis, consciousness, vision)
  3. Microangiopathic haemolytic anaemia (MAHA) (severe, often with jaundice)
  4. Thrombocytopenia (severe, often mucosal bleeding)
  5. Renal failure. Also: haematuria or proteinuria.
Pathogenesis: Adult are chiefly affected due to deficiency of specific metalloproteinase ADAMTS-13

  1. Idiopathic
  2. Drugs (eg clopidogrel, cyclosporin),
  3. Pregnancy, HIV, SLE.
Tests: As HUS. In both (HUS and TTP) - PT, PTT, fibrinogen concentration are normal.
DIC is not a feature.

Rx: It is a hematological emergency
  1. Urgent plasma exchange is life-saving. It is the treatment of choice.
  2. Steroids.

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