[Aquired immune hemolytic anemias]

Aquired immune hemolytic anemias are classified in autoimmune hemolytic anemia (AIHA) of warm type, cold agglutinine disease, paroxysmal cold hemoglobinuria, drug-induced immune hemolytic anemia, and paroxysmal nocturnal hemoglobinuria. The autoantibodies in AIHA of warm type react most strongly at 37 degrees C (warm autoantibodies). They are of the IgG, less commonly of the IgM and IgA classes. The cause of autoimmunization remains obscure in 50% of the patients (idiopathic AIHA). In the remaining cases, the AIHA is associated with other diseases. Corticosteroids are the mainstay of therapy, but most patients with AIHA of warm type require additional treatment with azathioprine or other drugs. Cold agglutinins are the cause of hemolysis in about 10% of patients with AIHA. Paroxysmal cold hemoglobinuria (Donath-Landsteiner) is less common and occur in children following infections. Drugs are the cause of hemolysis in about 10% of all cases with AIHA. The true incidence of alloimmune hemolytic anemias including neonatal immune hemolytic anemias is unknown. The paroxysmal nocturnal hemoglobinuria is rare. It is caused by complement activation due to aquired membrane defects.