[Autoimmune hemolytic anemia]

Autoimmune hemolytic Anemia (AIHA) is a uncommon but potentially lethal disorder requiring prompt diagnosis and treatment. Diagnosis is based on clinical and laboratory signs of hemolysis and a positive direct antiglobulin test (DAT). AIHA is classified according to the clinical context (primary or secondary) and the characteristics of the auto-antibody (warm vs. cold antibodies). Most AIHA are caused by warm antibodies and in about fifty percent of these patients an underlying disease such as a lymphoproliferative or an autoimmune disorder can be detected. Warm antibodies usually belong to the IgG type and cause hemolysis mainly by Fc-mediated phagocytosis of the IgG-coated red blood cells (RBC) in the spleen. First-line treatment is still based on systemic corticosteroids whereas second-line treatment options include the anti-CD20-antibody rituximab, splenectomy and various immunosuppressive drugs. Cold-agglutinines are less common and usually associated with an underlying disease such as infections (acute) or again lymphoproliferative and autoimmune disorders (chronic). Cold antibodies generally belong to the IgM type and are strong activators of the classical complement pathway which leads to intravascular hemolysis. Treatment options are usually supportive (warming) and RBC transfusions. Paroxysmal cold hemoglobinuria (bithermic IgG antibody) is an important cause of hemolysis in infants and occurs secondary to acute infections.