Cold Agglutinin Disease

Cold agglutinin disease (CAD) is a chronic autoimmune hemolytic anemia caused by a clonal B-cell disorder in the bone marrow. The clone usually produces an IgM cold agglutinin. In cooler peripheral blood, the antibody binds red blood cells and causes agglutination. It also activates the classical complement pathway. When blood returns to the warmer central circulation, antibody may detach while complement remains on the red-cell surface; complement-tagged cells are then cleared, producing hemolysis. This mechanism links the central findings: anemia and fatigue from red-cell loss, biochemical evidence of hemolysis, and cold-induced circulatory symptoms from agglutination. CAD is distinct from cold agglutinin syndrome (CAS), in which a similar cold-antibody hemolytic process occurs secondary to another condition such as an infection or overt lymphoma. Infection, major trauma, or major surgery can intensify complement activation and precipitate an acute exacerbation. Thermal protection is therefore supportive care, but the nurse should not assume that every deterioration is simply caused by cold exposure. Drug treatment targets either the pathogenic B-cell clone or the classical complement pathway and is selected by hematology according to the patient’s...