Shigella toxins produced by Escherichia coli O157:H7 and Shigella dysenteriae type I have been associated with the pathogenesis of HUS and thrombotic thrombocy-topenic purpura (TTP). Shigella toxins may exert a direct effect on platelets, increasing their likelihood of clumping and the toxins may have a local effect on endothelial cells, causing thrombus formation.
Increased platelet consumption may result from a generalized increase in platelet activation. Aggregates of platelets may then become trapped in the small blood vessels, resulting in damage to circulating erythrocytes and a microangiopathic hemolytic anemia.
• An infection, either mild or severe, associated with gastrointestinal symptoms, including vomiting and bloody diarrhea, precedes the development of HUS.
• The onset of oliguria associated with hypertension may lead to renal failure within days of the initial illness.
• Children between the ages of 4 months and 2 years are typically affected. It is less common in older children. It can give a picture very similar to TTP.
• Microangiopathic hemolytic anemia
• Reduced large multimers of von Willebrand factor (consumed during in vivo platelet aggregation)
• Decreased immunoglobulins in some patients
• Depleted prostaglandin I2 (PGI2) in some patients.
• Aggressive management of renal failure with fluid restriction and peritoneal dialysis, when indicated.
• Correction of anemia with red cell transfusion.
• Life-threatening bleeding due to thrombocytopenia is uncommon. Platelet transfusions can worsen thrombotic complications of the illness and should not be given to a patient with HUS.
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