Red blood cell agglutinins are autoantibodies that cause red blood cell clusters to form and can create anemia by accelerating their destruction. The presence of agglutinated red blood cells in clusters can also lead to false low red blood cell counts when the blood count is analyzed. Agglutinin levels in red blood cells are assessed under a microscope on a drop of blood, and results are expressed from “light” to 4+ (four plus). A high agglutinin level requires taking another red blood cell count, sometimes after replacing the blood plasma (which contains agglutinins) with water. Often these agglutinins are called “cold agglutinins” because they have the property of producing red blood cell clusters only when the skin is exposed to cold temperatures.
Cold agglutinin disease can be “primary” or “secondary” to another disease, such as infectious mononucleosis, a respiratory tract infection with mycoplasma pneumonia or other bacterial, viral or parasitic infections. More rarely, some forms may also be associated with cancers such as lymphoma, leukemia or multiple myeloma.