Which form of immune hemolytic anemia is most active at temperatures below 30°C?

Which form of immune hemolytic anemia is most active at temperatures below 30°C?

• A. Cold agglutinin disease
• B. Warm autoimmune hemolytic anemia
• C. G6PD deficiency
• D. Hereditary spherocytosis

Answer: (A)

Cold agglutinin disease is driven by autoantibodies that react best at cold temperatures, typically below 30°C. These antibodies are usually IgM and bind to red blood cells in the cooler parts of the body (like the fingers or toes), causing the cells to agglutinate and activating the classical complement pathway. Complement activation can lead to hemolysis, especially when the blood is warmed again and the coated cells are cleared. This temperature dependence distinguishes it from other conditions. Warm autoimmune hemolytic anemia involves IgG antibodies that bind red cells at normal body temperature and are cleared mainly by splenic macrophages, not by cold temperatures. G6PD deficiency is not immune-mediated; it causes hemolysis in response to oxidative stress (certain drugs, infections) rather than temperature. Hereditary spherocytosis is a structural red cell membrane defect leading to extravascular hemolysis, not antibody-mediated or temperature-dependent.

Cold agglutinin disease is driven by autoantibodies that react best at cold temperatures, typically below 30°C. These antibodies are usually IgM and bind to red blood cells in the cooler parts of the body (like the fingers or toes), causing the cells to agglutinate and activating the classical complement pathway. Complement activation can lead to hemolysis, especially when the blood is warmed again and the coated cells are cleared. This temperature dependence distinguishes it from other conditions.

Warm autoimmune hemolytic anemia involves IgG antibodies that bind red cells at normal body temperature and are cleared mainly by splenic macrophages, not by cold temperatures. G6PD deficiency is not immune-mediated; it causes hemolysis in response to oxidative stress (certain drugs, infections) rather than temperature. Hereditary spherocytosis is a structural red cell membrane defect leading to extravascular hemolysis, not antibody-mediated or temperature-dependent.