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Cold autoimmune hemolytic anemia comprises two types of autoimmune hemolytic anemia (AIHA; see this term) defined by the presence of cold autoantibodies (autoantibodies which are active at temperatures below 30°C): cold agglutinin disease (CAD), which is the more common, and paroxysmal cold hemoglobinuria (PCH; see these terms). CAD is more common in people over the age of 55 years, while PCH typically presents in young children. CAD is caused by IgM autoantibodies while PCH is caused by an IgG immunoglobulin. |