Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome in children and adolescents.

Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are both uncommon disorders that present with a microangiopathic hemolytic anemia and thrombocytopenia. Although for TTP, neurologic manifestations predominate, and in HUS renal dysfunction is virtually always present, there is significant overlap in their clinical presentation. In recent years, tremendous progress has been made in our understanding of the pathogenesis of these disorders. It is now apparent that there are subcategories of both TTP and HUS that can differ in their clinical manifestations, etiology, and management. For instance, although most cases of HUS are due to infection with organisms that produce Shiga-like toxin, other cases may be caused by defined genetic abnormalities. Similarly, TTP is usually caused by genetic or acquired deficiency of the ADAMTS13 enzyme; however, in other cases the relationship with this enzyme remains to be established. Management includes supportive care, plasma transfusions for genetic protein deficiencies, and plasma exchange transfusion for autoimmune TTP.