Cold Agglutinin Disease (CAD)

Cold agglutinin disease (CAD) is a rare form of autoimmune hemolytic anemia (AIHA) in which autoantibodies target antigens attached to the surface of erythrocytes. AIHAs are subdivided into warm, cold, and mixed types; the type is determined by the thermal amplitude test, which measures the highest temperature at which the autoantibodies, usually of the immunoglobulin M (IgM) subclass, bind to erythrocytes.1 

The binding of cold agglutinins to the surface of erythrocytes causes the erythrocytes to agglutinate at colder temperatures. The antigen-antibody complex thus formed drives complement activation and intravascular and extravascular hemolysis of the involved erythrocytes.2 

Disease caused by warm or cold circulating autoantibodies is classified as “primary” if it is idiopathic and as “secondary” when an underlying condition such as infection or malignancy can be identified as the cause.1 CAD accounts for approximately  15% of all cases of AIHA, affecting 1 in every 1 million individuals per year.3   

History of CAD

CAD was first described by Karl Landsteiner in 1903 in a book titled Über Beziehungen zwischen dem Blutserum und den Körperzellen (“About Relationships Between the Blood Serum and the Body Cells”), in which he explained blood agglutination due to cold temperatures.3,4 

Following Landsteiner’s discovery, Clough and Richter, in a 1918 Johns Hopkins Hospital publication, associated cold agglutination with the hemolysis of erythrocytes and proposed a connection with respiratory tract infections.3,5 In 1937, Rosenthal and Corten further described the association of CAD with erythrocyte hemolysis.2 In 1943, Horstmann and Tatlock discovered cold agglutinins in the blood serum of patients with primary atypical pneumonia.3 Some 50 years following Landsteiner’s publication, Schubothe coined the term “cold agglutinin disease.”2

In 1956, Wiener and colleagues used bovine red blood cells in a biological test to identify an antibody, which they termed “anti-I,” in an individual with CAD.6 At about the same time, in 1957, Christenson and Dacie identified the monoclonal protein with antibody activity responsible for CAD. They discovered that when serum containing I-antigen erythrocytes was incubated, the monoclonal proteins could be removed.3,7,8 

In 1960, Marsh and Jenkins commented that 5 types of antigen, called “i cells,” had been identified in addition to the predominant I antigen found on the surface of erythrocytes. They described 2 unique cases in which the patients’ sera agglutinated adult I-negative (i) cells strongly but agglutinated normal (I) adult cells weakly.3,9 

Development of CAD Treatment

Other than the recommendation that patients with CAD avoid the cold, CAD has been treated with rituximab since the late 1990s. Rituximab is a monoclonal antibody that targets CD20, which is a membrane-embedded B-cell marker surface molecule that plays a crucial role in the development and differentiation of B cells into plasma cells.1,10 Therefore, rituximab reduces the population of lymphocytes that produce the IgM autoantibodies responsible for 90% of cases of CAD.11 

In 2004, a study by Berentsen and colleagues reported a complete or partial response in at least 60% of a group of patients with primary chronic CAD treated with rituximab (median increase in hemoglobin concentration of 4 g/dL [40 g/L]), indicating the efficacy of rituximab against erythrocyte hemolysis. The median time to response was 1.5 months (mean, 1.7; range, 0.5-4.0), and the median duration of treatment was 11 months (mean, 13; range, 2-42).1,12

In 2006, a study by Schöllkopf and colleagues reported that 9 of 20 patients (45%) with chronic CAD had experienced a complete or partial response to rituximab, with a median time to response of 3 months. In their abstract, the authors detailed previous disappointing results with several therapeutic modalities for CAD, including interferon, prednisolone, and alkylating cytostatics.1,13 

Prednisone is successfully used to treat warm AIHA and affects IgG antibody production rather than IgM production, so that it is ineffective as a treatment for CAD. Plasma exchange and splenectomy are also ineffective treatments for CAD.11 

An ongoing clinical trial is investigating the possible use of sutimlimab to prevent complement deposition on the surface of erythrocytes, thereby prolonging the lifespan of circulating erythrocytes. Phase 1 data have indicated significant improvements in the hemoglobin level and hematocrit of all patients enrolled in the trial.11


  1. Gabbard AP, Booth GS. Cold agglutinin disease. Clinical Hematology International. 2020;2(3):95-100. doi:10.2991/chi.k.200706.001
  2. Gupta V. Assessment of red blood cell parameters and peripheral smear at different temperatures in case of cold agglutination disease. Ann Med Health Sci Res. 2014;4(Suppl 1):S25-S28. doi:10.4103/2141-9248.131703
  3. Swiecicki PL, Hegerova LT, Gertz MA. Cold agglutinin disease. Blood. 2013;122(7):1114-1121. doi:10.1182/blood-2013-02-474437 
  4. Landsteiner K. Über Beziehungen zwischen dem Blutserum und den Körperzellen. Munch Med Wochenschr. 1903;50:1812-1814. 
  5. Clough MC, Richter IM. A study of an auto-agglutinin occurring in a human serum. Johns Hopkins Hosp Bull. 1918;29:86-93.
  6. Wiener AS, Unger LJ, Cohen L, Feldman J. Type-specific cold auto-antibodies as a cause of acquired hemolytic anemia and hemolytic transfusion reactions: biologic test with bovine red cells. Ann Intern Med. 1956;44(2):221-240. doi:10.7326/0003-4819-44-2-221
  7. Christenson WN, Dacie JV, Croucher BE, Charlwood PA. Electrophoretic studies on sera containing high-titre cold haemagglutinins: identification of the antibody as the cause of an abnormal gamma 1 peak. Br J Haematol. 1957;3(3):262-275. doi:10.1111/j.1365-2141.1957.tb05795.x
  8. Dacie JV, Crookston JH, Christenson WN. Incomplete cold antibodies’ role of complement in sensitization to antiglobulin serum by potentially haemolytic antibodies. Br J Haematol. 1957;3(1):77-87. doi:10.1111/j.1365-2141.1957.tb05773.x
  9. Marsh WL, Jenkins WJ. Anti-i : a new cold antibody. Nature. 1960;188(4752):753-753. doi:10.1038/188753a0
  10. CD20. ScienceDirect. Accessed September 8, 2021.
  11. Broome CM. Diagnosis and treatment of cold agglutinin disease. Clin Adv Hematol Oncol. 2019;17(3). 
  12. Berentsen S, Ulvestad E, Gjertsen BT, et al. Rituximab for primary chronic cold agglutinin disease: a prospective study of 37 courses of therapy in 27 patients. Blood. 2004;103(8):2925-2928. doi:10.1182/blood-2003-10-3597
  13. Schöllkopf C, Kjeldsen L, Bjerrum OW, et al. Rituximab in chronic cold agglutinin disease: a prospective study of 20 patients. Leukemia Lymphoma. 2006;47(2):253-260. doi:10.1080/10428190500286481

Reviewed by Debjyoti Talukdar, MD, on 9/9/2021.