Author and Editor Disclosure

Synonyms and related keywords: cold agglutinin hemolytic anemia, cold agglutinin disease (CAD), acrocyanosis, cold-induced immune hemolytic anemia, mixed autoimmune hemolysis, Mycoplasma pneumoniae, M pneumoniae, infectious mononucleosis, Epstein-Barr virus, EBV, influenza, human immunodeficiency virus, HIV, cytomegalovirus, CMV, rubella, varicella, varicella zoster virus, mumps, hemolytic anemia, subacute bacterial endocarditis, syphilis, malaria, equestrian perniosis, lymphoma, Waldenström syndrome, chronic lymphocytic leukemia, CLL, lymphoproliferative disease, autoimmune disease, myeloma, Kaposi sarcoma, Kaposi's sarcoma, angioimmunoblastic lymphoma

Background

In 1903, Landsteiner was the first to describe the presence of cold agglutinins in the blood, which were capable of agglutinating RBCs (Landsteiner, 1903). He described the finding of a low titer of these agglutinins in healthy individuals. Later, the appearance of the I antigen on human RBCs in the postnatal period due to modification of the fetal i antigen structure (a change occurring over the first 18 mo) was found to lead to the development of low levels of anti-I agglutinins. These antibodies induce hemagglutination mainly at 4°C and not at 37°C and were therefore termed cold agglutinins.

Subsequent observations have led to the understanding that cold agglutinins are usually immunoglobulin M (IgM) antibodies (less commonly immunoglobulin A [IgA] or immunoglobulin G [IgG]) that may result in hemolytic anemia due to complement-mediated RBC destruction in the reticuloendothelial system. Slowing of blood flow with occlusion of superficial blood vessels by agglutinated RBCs can cause a Raynaudlike syndrome (acrocyanosis) (Schobuthe, 1952; Schobuthe, 1966; Dacie, 1992).

Pathophysiology

Cold agglutinin disease (CAD) usually develops as a result of the production of a specific IgM antibody directed against the I/i antigens (precursors of the ABH and Lewis blood group substances) on RBCs. These cold agglutinins commonly have variable heavy-chain regions encoded by V_H (Harboe, 1965; Angevine, 1966; Garraty, 1977; Wortman, 1979; Petz, 1980; Rosse, 1980; Roelke 1981; Crisp, 1982; Sokol, 1983; Roelke, 1984; Dacie, 1992; Agarwal, 1995; Packman, 1995; Jacobs, 1996; Terness, 1997; Thorpe, 1998; Ciejka, 1999; De Silva, 2000), with a distinct idiotype identified by the 9G4 rat murine monoclonal antibody (Dacie, 1992). This 9G4 idiotope is localized to the V4-34 encoded portion of the variable region (Potter, 2000). It is found on cold agglutinin-producing malignant lymphoid cells in the bone marrow in persons with lymphoproliferative disorders, on a small proportion of normal lymphoid cells, and in the spleen of a 15-week-old fetus.

The V_H genes appear to regulate not only the production of cold agglutinins, but also the formation of normal antibodies to other carbohydrate antigens, both sharing the same fundamental mechanism of production. The I/i antigen analogs are present on human lymphocytes, neutrophils, and monocytes and in human saliva, milk, and amniotic fluid. Thus, in disease states, the finding of a clone of B cells producing this antibody may be the result of expansion of a normal clone that is specific for the production of an immunoglobulin with these properties. Autoimmune and lymphoproliferative disorders can also be associated with the production of cold agglutinins.

In addition, some polyclonal IgM cold agglutinins arise in association with Mycoplasma pneumoniae infections, infectious mononucleosis, influenza B, human immunodeficiency virus (HIV), and other infections. Cytomegalovirus (CMV), rubella virus, varicella-zoster virus, Parvovirus B19, and Chlamydia psittaci have also been implicated (McNicholl, 2000). In the case of infectious mononucleosis, hemolysis tends to develop 1-2 weeks after the onset of illness but may occur simultaneously or up to 2 months after onset (McNicholl, 2000). Furthermore, increased expression of both I/i antigens have been described on hemoglobin SS erythrocytes, which suggests that such patients may have increased susceptibility to cold-mediated hemolysis (Maniatis, 1979).

In its classic presentation, with hemolytic anemia and Raynaud syndrome, CAD is usually idiopathic. As with most autoimmune diseases of a chronic nature, stimulated B lymphocytes begin to produce pathogenic antibodies against an antigen normally present in human tissue. In this disease, the antibody is an IgM, usually monoclonal, with kappa or lambda light chains. In chronic CAD, the antibody is usually directed against the I antigen on the membrane of normal adult RBCs.

Uncommonly, the antibody may be directed against only the i antigen found on fetal cord blood RBCs, which lack the mature I antigen; this has been reported in association with infectious mononucleosis (Petz, 1980). In a study of 78 patients, κ light-chain specificity was found in the majority of patients with chronic CAD or Waldenström macroglobulinemia, whereas two thirds of cold agglutinins found in patients with lymphomas had light-chain specificity. The type of light chain appears to correlate with the antigen specificity of the cold agglutinin.

Fifty-eight percent of IgM/κ (usually κIII variable region subgroup) were anti-I, but 75% of IgM/λ had other antigen specificities (Crisp, 1982). Antigen specificities of cold agglutinins other than the I/i system that have been described include those against Pr, M, P, and Lud and anti-Gd, anti-Fl, and anti-Sa (Angevine, 1966; Roelke 1981; Roelke, 1984). Exclusive occurrence of κ chains has also been shown with some cold agglutinins (Harboe, 1965). Thus, benign and malignant cold agglutinins exhibit differences in their light chains and their specificities toward membrane antigens.

In vivo, the IgM antibody attaches to RBCs and causes them to agglutinate at temperatures below 37°C and maximally at 0-5°C, resulting in impaired blood flow to the digits, nose, and ears, ie, areas more likely to have colder temperatures (in the 30°C range) when exposed to the cold. Fixation of the C3 component of complement to the RBC by the cold agglutinin usually occurs in vivo at higher temperatures compared to those required by the IgM cold agglutinin to attach to the RBC, but generally less than 31°C. When the IgM/C3b-coated RBC circulates to warmer tissues, the IgM dissociates, leaving complement C3b on the original RBC.

The dissociated IgM cold agglutinin can then bind to another RBC at lower temperatures. Fixation of complement results in C3b and/or C4b components on the RBC membrane, which may lead to phagocytosis by macrophages in the reticuloendothelial system, particularly in the liver, where the macrophages have specific complement receptors. With time, the C3b components are converted enzymatically to C3dg, which is not recognized by macrophage receptors.

In chronic CAD, complement tends to be depleted. Thus, the hemolysis is self-controlled, and anemia may only be mild or moderate because these C3dg-coated RBCs are no longer capable of reacting with the IgM antibody in the cold, the C3dg-coated RBCs are not recognized by the macrophages, and low complement levels become rate limiting.

Temporary increases in complement levels, as can occur with intercurrent febrile illnesses, can increase hemolysis. Lytic components of complement C5-C9 generally do not form on these cells, and intravascular hemolysis by complement is less likely to occur (Packman, 1995). Hemolysis develops acutely following M pneumoniae infections and lasts approximately 1-3 weeks. Subclinical mild hemolysis with reticulocytosis also may occur, and the results of a direct Coombs test may be weakly positive, especially with M pneumoniae infections.

Monoclonal cold agglutinin IgM antibodies found in patients with lymphoma are the product of the abnormal clone. Progression of an idiopathic CAD to malignant lymphoma may occur in some cases; thus, affected patients require close long-term follow-up, with obvious therapeutic implications (Petz, 1980; Roelke, 1984). One study of 86 patients in Norway showed clonal light chain predominance in 90% of patients, evidence of lymphoplasmacytic lymphoma in 50%, and lymphoma of any type in 76% overall (Gertz, 2006).

Hemolysis due to cold agglutinins can sometimes be accompanied by a warm antibody (IgG), resulting in a mixed autoimmune hemolytic anemia (Petz, 1980; Sokol, 1983), ie, cold agglutinin syndrome and warm antibody autoimmune hemolysis, with the direct antiglobulin (direct Coombs) test results positive for the presence of both IgG and complement on the surface of the sensitized RBC. In mixed antibody syndromes, the IgG and IgM antibody components can be separated. The cold autoantibodies reactive at temperatures of 30°C or higher often show blood group specificity to the adult I antigen, while the warm autoantibodies are not directed against this system. A combination of cold agglutinins and cryoglobulins has also been reported with an IgM κ monoclonal antibody with specificity to the Pr2 antigen system (Ciejka, 1999).

Several factors play a role in determining the ability of a cold agglutinin to induce an active hemolytic anemia. These factors include the ability to initiate; the extent of antibody-induced complement activation; the concentration of the antibody; the range of temperatures, including the highest temperature at which the antibody interacts with the RBC (its thermal amplitude); the qualitative binding of IgM to the red cell; and modification of the antibody's ability to fix complement components onto the RBCs (Rosse, 1980; Gertz, 2006). In addition, the presence of biphasic hemolysins implicates more severe disease. Biphasic haemolysins bind to red blood cells at low temperatures and activate complement to produce in vitro hemolysis at warmer temperatures (37°C), whereas monophasic hemolysins bind to red cells and activate complement at the same temperature (Sokol, 2000).

In vitro studies have shown that human monoclonal antibodies encoded by the V4-34 gene segment not only have cold agglutinin properties, but also exhibit multireactivity. This is in contrast to the generally monospecific I/i reactivity of sera from patients with CAD (Thorpe, 1998). Data have confirmed an immunomodulatory/immunosuppressive role of the naturally occurring anti-F(ab')₂ antibodies in the production of cold agglutinins, with an inverse correlation between the titers of IgG-anti-F(ab')₂ and cold agglutinins (Terness, 1997). This inverse correlation was found only in patients with anti-I/i and in the presence of a monoclonal lymphocyte population.

Frequency

United States

Low titers of cold agglutinins (1:64 or less) reactive at low temperatures are commonly found in the sera of healthy persons. Postinfectious elevations in the cold agglutinin titers (eg, M pneumoniae, Epstein-Barr virus [EBV], cytomegalovirus [CMV]) are transient. Cold agglutinins develop in more than 60% of patients with infectious mononucleosis, but hemolytic anemia is rare. Development of the CAD syndrome is relatively uncommon, at least in the classic chronic form. Various reports state that 7-25% of cases of autoimmune hemolytic anemia are cold agglutinin–mediated. Incidence of both cold and warm autoimmune hemolytic anemia (combined) is approximately 1 in 80,000; the incidence of CAD, which is approximately one fourth of the total, is approximately 1 in 300,000. Among autoimmune hemolytic anemias, CAD is the second most common cause, after warm autoantibody–induced immune hemolysis.

International

Data regarding incidence of CAD are lacking. Frequency figures listed for the United States probably also apply to Canada and the United Kingdom.

Mortality/Morbidity

Morbidity in chronic CAD is usually limited to symptoms precipitated by exposure to the cold. Transfusions for life-threatening symptoms due to severe anemia require prewarming and the use of washed RBCs (not cold). Occasionally, peripheral gangrene and, rarely, fatalities, have occurred after inadvertent and perhaps prolonged exposure to the cold.

Race

A racial predilection has not been reported.

Sex

Women are affected more commonly than men (Petz, 1980; Dacie, 1992). Mixed autoimmune hemolysis has a male-to-female ratio of 1:1.5.

Age

Infants and children are rarely affected with chronic CAD, although M pneumoniae and infectious mononucleosis are diseases of young persons. Chronic CAD appears to affect adults who are of middle age and older, with an average age more commonly older than 60 years (peaking in the seventh and eighth decades of life). Although found in persons of all age groups, mixed autoimmune hemolysis is also more frequent in later life.

History

• A common complaint is painful fingers and toes with purplish discoloration associated with cold exposure. In chronic CAD, the patient is more symptomatic during the colder months.



• Cold agglutinin–mediated acrocyanosis differs from Raynaud phenomenon. In Raynaud phenomena, caused by vasospasm, a triphasic color change occurs from white to blue to red based on vasculature response; no evidence of such a response exists in CAD(McNicholl, 2000).



• Chronic fatigue may also be a complaint, due to the anemia during those periods.



• Respiratory symptoms may be present in patients with M pneumoniae infection.



• Hemoglobinuria (the passage of dark urine that contains hemoglobin) may be rarely reported following prolonged exposure to cold; this is a result of hemolysis. This is more commonly seen in paroxysmal cold hemoglobinuria.



• Other symptoms are related to the underlying disease state associated with the production of cold agglutinins. The severity of the clinical manifestations of the cold agglutinins themselves varies from an inconsequential laboratory finding in the benign variety to serious manifestations, such as acute hemolytic crises and Raynaud-type phenomena, with the more malignant variety.



• History of weight loss, adenopathy, and other symptoms relate to the associated disease state.

Physical

• Physical examination may reveal nothing unusual or only pallor, unless the patient is observed during or shortly after cold exposure. Purplish discoloration of the ears, forehead, tip of the nose, and digits may then be observed.



• Ischemic necrosis can lead to pain, but skin ulceration secondary to ischemia is uncommon.



• Splenomegaly and jaundice, characteristic of lymphoproliferative disorders or infectious mononucleosis, may sometimes be observed in those with chronic CAD but are usually absent.



• Lymphadenopathy, fever, or both may be present in patients with lymphoma, infectious mononucleosis, or other infections.



• Pulmonary signs such as rales and fever may be found in patients with mycoplasmal pneumonia (Schobuthe, 1966; Petz, 1980, Packman, 1995). Other findings, including hepatomegaly, relate to the presence of underlying or associated disease states.

Causes

• Classic chronic CAD is idiopathic, associated with symptoms and signs in relation to cold exposure.



• Rarely, the first manifestations develop when the patient is subjected to hypothermia for cardiopulmonary bypass surgery (Agarwal, 1995).



• Transient acute hemolysis may occur secondary to certain infectious diseases, such as M pneumoniae infection and infectious mononucleosis (eg, EBV) infections. Other viral infections, such as influenza, HIV, CMV, rubella, varicella, and mumps, have been reported to be associated with a hemolytic anemia due to cold agglutinins. Other associated illnesses include subacute bacterial endocarditis, syphilis, and malaria. The development of a febrile illness in a patient with chronic CAD also may accelerate hemolysis.



• Cold agglutinins are seen in CANOMAD syndrome (CANOMAD is an acronym for chronic ataxic neuropathy ophthalmoplegia M-protein agglutination disialosyl antibodies). CANOMAD syndrome is described by gait and upper-limb ataxia; cranial nerve involvement with external ophthalmoplegia; and the presence of cold agglutinins, IgM paraprotein, and anti-disialosyl antibodies (Delval, 2006). Both the neurologic and hematologic symptoms have been seen to respond to rituximab (Siddiqui, 2003).



• Equestrian perniosis is a rare cause of persistent elevated titers of cold agglutinins (De Silva, 2000).



• An idea of associated disease distribution is provided by a study of 78 patients with persistent cold agglutinins. Of these, 31 had lymphoma, 13 had Waldenström syndrome, 6 had chronic lymphocytic leukemia, and 24 had chronic idiopathic CAD (Crisp, 1982). Thus, lymphoproliferative and autoimmune diseases, myeloma, Kaposi sarcoma, and angioimmunoblastic lymphoma may occasionally be associated with the production of cold agglutinins. Nonhematologic malignancies can occasionally be associated with a high-titer cold agglutinin–induced hemolytic anemia (Wortman, 1979).



• Cytogenetic studies in patients with CAD have revealed the presence of trisomy 3 and trisomy 12. Translocation (8;22) is also reported in association with CAD (Gertz, 2006; Michaux 1998; Chang, 2004).



• Cold agglutinin–mediated hemolytic anemia has been described in patients after living donor liver transplant treated with tacrolimus and after bone marrow transplant with cyclosporine treatments. It is postulated that such calcineurin inhibitors, that selectively affect T-cell function and spare B-lymphocytes, may interfere with the deletion of autoreactive T-cell clones, resulting in autoimmune disease. (Kitamura, 2003; Tamura, 1994; Thomson, 1995).



• CAD has been described in patients with sclerodermic features in which the degree of anemia is associated with increasing disease activity of the patient’s systemic sclerosis. This may suggest a close association between systemic rheumatic disease and autoimmune hematological abnormalities (Oshima, 2004).



• Hyperreactive malarial splenomegaly (HMS) is an immunopathological complication of recurrent malarial infection. Patients with HMS develop splenomegaly, acquired clinical immunity to malaria, high serum concentrations of anti-Plasmodium antibodies, and high titers of IgM, with a complement-fixing IgM that acts as a cold agglutinin (Torres, 2002).



• Vaccination with diphtheria-pertussis-tetanus (DPT) vaccination has been implicated in the development of autoimmune hemolytic anemia caused by IgM autoantibody with a high thermal range. A total of 6 cases have been reported; 2 followed initial vaccination and 4 followed the second or third vaccinations (Johnson, 2002; Gedikoglu, 1967; Bossi, 1972; Zupanska, 1976; Haneburg, 1978).

Cholangitis

Other Problems to be Considered

• Cryoglobulinemia: This condition has almost none of the features of CAD except for a history of Raynaud syndrome and an elevated IgM level in some cases, but without hemolysis.



• Warm antibody–mediated autoimmune hemolytic anemia (AIHA): This must be differentiated from CAD, especially when no symptoms or findings suggest cold-induced acrocyanosis or Raynaud-type phenomenon. The cold agglutinin titer is a specific differentiating test, and a positive IgG-specific Coombs test result would exclude CAD. Examination of the peripheral blood smear is less specific, but finding typical RBC clumps would be unlikely in AIHA, unless it is a mixed IgG-IgM warm/cold autoimmune hemolytic anemia (Sokol, 1983; Packman, 1995).



• Episodic hemoglobinuria following cold exposure: This can occur in more severe cases of CAD, so that confusion may exist as to whether it is paroxysmal cold hemoglobinuria (PCH) or CAD. The cold agglutinin titer is less than 1:64 in PCH, and the result of the Donath-Landsteiner test for cold hemolysis is positive. The age of the patient is very important; a diagnosis of PCH is more probable in a child (Petz, 1980). March hemoglobinuria (episodic) is clearly related to exertion.



• Neoplasms, especially of the lymphoid type: These may be associated with a cold agglutinin or a cryoglobulin, giving rise to symptoms of Raynaud syndrome. If the cold agglutinin titer is elevated and a complement-specific Coombs test result is positive, the patient may have a neoplastic clone of lymphocytes producing the CAD. This would be important in terms of therapy and prognosis because the underlying lymphoma may be responsive to treatment. Often, the more severe forms of CAD are associated with lymphoid malignancy (Hamblin, 2000).



• Drug-induced immune hemolytic anemia: This condition may be a source of confusion, particularly when the direct Coombs test result is positive only for complement, but the specific drug use and low cold-agglutinin titer should help to distinguish it from CAD.



• Rheumatologic diseases manifesting Raynaud syndrome



• Heparin-induced thrombocytopenia/thrombosis syndrome: Patients may have painful digits. Anemia could be due to bleeding, but other manifestations are different.



• Systemic vasculitis, sometimes with hemolysis (systemic lupus and scleroderma)



• Erythromelalgia in association with primary thrombocythemia and painful fingers and toes



• Drug-induced hemolytic anemia: A positive result from the Coombs test (methyldopa) is possible.



• Infections (eg, malaria)

Lab Studies

• CBC count with differential leukocyte count and platelet count
• • If the cold agglutinin is operative at room temperatures, then falsely high mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration with a low RBC count are obtained due to agglutination of RBCs in the cold, automated counter.
  
  
  
  • Agglutination also may be seen in anticoagulated blood at room temperature. This agglutination worsens with storage and cooling of blood to 4°C and disappears rapidly upon warming the blood to 37°C, unlike with rouleaux formation. Repeating the CBC count after warming the blood to 37°C avoids this problem. Thus, the clinical laboratory is frequently the first to report the presence of a cold agglutinin. Agglutination in the cold also may interfere with typing and cross-matching of blood.
  
  
  
  • Review of a peripheral blood smear may reveal the presence of RBCs in clumps (see Image 1).
  
  
  
  • In those with chronic CAD, a mild-to-moderate stable anemia is present. Occasionally, the anemia is severe.
  
  
  
  • Leukocytosis may be evident during hemolytic episodes.
     
• Reticulocyte count
• • The results of the count are usually increased, with polychromasia in the peripheral blood smear.
  
  
  
  • Spherocytes may be present, although less prominently than in warm autoantibody–induced hemolytic anemias.
     
• Urinalysis
• • Perform urinalysis with microscopic assessment for RBCs and a chemical test for hemoglobin to differentiate between hematuria and hemoglobinuria.
  
  
  
  • Processing only fresh urine samples is important to avoid in vitro hemolysis of RBCs in the urine, leading to an incorrect diagnosis of hemoglobinuria.
  
  
  
  • Urine immunoelectrophoresis should be performed if serum globulins are abnormal; only a 24-hour urine sample can be used to conclusively exclude the presence of light chains.
     
• Biochemical tests of the serum and plasma
• • Lactic dehydrogenase and total and direct bilirubin values are elevated, depending on the extent of hemolysis.
  
  
  
  • The haptoglobin level may be reduced when hemolysis is active and ongoing with an intravascular spillover from a massive extravascular process and in the absence of significant liver disease.
     
• Serum electrophoresis and serum immunoelectrophoresis
• • Perform serum protein electrophoresis and serum immunoelectrophoresis (immunofixation) as initial tests to look for a dysproteinemia.
  
  
  
  • Quantitation of serum levels of IgG, IgA, and IgM should follow when a dysproteinemia is suggested based on results from the first 2 tests. These test results may be normal or abnormal (increased IgM with kappa or lambda light chains).
  
  
  
  • Careful sample processing, avoiding exposure of blood to the cold, and maintaining it at 37°C prior to testing is essential. If the blood sample is cooled and not kept warm from the time it is collected to the time it is tested, the cold agglutinin attaches to the RBCs and is removed from the serum, with a false-negative result.
     
• Special tests
• • The Direct Coombs test (DAT, direct antiglobulin test) should be performed with samples at 35-37°C, using polyspecific and monospecific Coombs sera, including monospecific anti-C3 and IgG antisera.
  
  
  
  • With the cold agglutinin titer, a titer of greater than 1:64 is considered abnormal when blood is tested at 4°C. Obtain the cold agglutinin titers also at 30°C and 37°C when needed. Testing at temperatures higher than 4°C is extremely valuable, particularly if the patient is to undergo hypothermia for surgery. CAD is usually associated with very high cold agglutinin titers of greater than 1:10,000 at 4°C, with a thermal amplitude of up to 30-32°C. The addition of bovine serum albumin (BSA) while testing for the cold agglutinin titer and thermal amplitude results in a better correlation with clinical hemolytic anemia compared to when data are obtained in the absence of BSA, using saline-suspended cells (Garraty, 1977).
  
  
  
  • Donath-Landsteiner screening tests are warranted only if hemoglobinuria is detected.
  
  
  
  • Cryoglobulin levels should be tested only if vascular purpura or other atypical findings such as elevated levels of IgM and/or hepatitis virus antibodies are found. Again, proper handling of the sample, by keeping it warm until the test is run, is essential to avoid premature loss of the cryoglobulin.
  
  
  
  • Perform tests for infectious diseases if such are considered.
    
    
    • Infectious mononucleosis (EBV)
    
    
    
    • Anti-influenza antibody
    
    
    
    • Anti–mycoplasmal pneumonia antibodies
    
    
    
    • HIV antibodies
    
    
    
    • Antihepatitis antibodies
    
    
    
    • CMV antibodies
    
    
    
    • Review of thick and thin smears for malaria as indicated
       
  • Perform blood tests for collagen vascular disease if the condition is a possibility.
    
    
    • Systemic lupus erythematosus
    
    
    
    • Rheumatoid arthritis
    
    
    
    • Scleroderma (systemic sclerosis)

Imaging Studies

• Perform a chest radiograph if pneumonia is suggested. Findings may also indicate lymphadenopathy.
• Computed tomography scans of the chest and abdomen are performed to assess for lymphadenopathy and splenomegaly when lymphoma is suggested.

Procedures

• Perform bone marrow aspiration and biopsy only when needed to exclude certain neoplastic or immunoproliferative diseases. Flow cytometry studies of bone marrow are helpful to define the presence of an abnormal monoclonal population of lymphocytes.
• A lymph node biopsy is necessary when unexplained lymphadenopathy is present. Fine-needle aspiration is not reliable compared to excision of the largest lymph node for diagnostic purposes because nodal architecture is important to making an accurate diagnosis and is preserved in a lymph node biopsy. The addition of flow cytometry to define the presence of abnormal monoclonal lymphocyte population(s) is also useful.

Histologic Findings

Depending on the underlying precipitating illness, changes may be seen in the bone marrow and lymph nodes. The presence of a malignant lymphoproliferative disorder also may be evident in these biopsy samples. Clumps of RBCs may be observed in the peripheral smear, as is discussed in Lab Studies (see Image 1).

Staging

Staging is applicable only if an underlying malignant disorder is present.

Medical Care

CAD may be managed successfully using protective measures (clothing) alone in most cases. Special protective clothing is sometimes necessary in extreme cases. Therapy is directed at serious symptoms and the underlying disorder, if any is found.

• In general, keep in mind that the idiopathic variety is generally a benign disease with prolonged survival and spontaneous exacerbations and remissions in the course of the disease.
  
  
  • Treatment depends on the gravity of the symptoms as determined by the characteristics of the antibody and the presence of associated disease(s).
  
  
  
  • Glucocorticoids are generally not useful in IgM-induced CAD but may occasionally work if an underlying warm antibody–induced hemolytic anemia is present or if a high thermal amplitude, low titer cold agglutinin is present or (rarely) when a cold reactive IgG antibody is produced.
  
  
  
  • The possibility of missing a lymphoproliferative disorder if glucocorticoids are used before obtaining necessary biopsies should be kept in mind.
  
  
  
  • The authors currently do not recommend the use of chemotherapeutic or immunosuppressive agents in the routine management of idiopathic CAD because of its basic benign nature.
     
• Acute postinfectious syndromes usually resolve spontaneously.



• Anemia is generally mild. Only patients who have serious symptoms related to anemia or have a Raynaud-type syndrome that constitutes a threat to life or quality of life require active therapy. The presence of an associated malignancy requires specific therapy.



• Chemotherapeutic agents should be used under appropriate circumstances, such as for an associated malignancy.



• When the disease is chronic and idiopathic, one must weigh the need for therapy, as dictated by the severity of the symptoms, versus the potential long-term serious consequences of chemotherapeutic or other agents used to treat monoclonal lymphoid populations. Such decisions should be made in close collaboration with well-informed patients and their families.
  
  
  • The authors advise extreme caution in selecting any chemotherapeutic or other immunosuppressive agents for the treatment of idiopathic CAD because of the potential long-term effects of these agents on the bone marrow stem cells and leukemogenic effects of alkylating agents. The authors believe that such agents are not usually needed in the treatment of patients idiopathic CAD.
  
  
  
  • If the use of glucocorticoids is contemplated, keep in mind that all necessary biopsies should be performed prior to the start of therapy.
     
• Plasmapheresis effectively removes and reduces the concentration of IgM antibody from plasma temporarily. This procedure is valuable for emergencies and allows time for drugs to have an effect, or it can be used to prepare patients for hypothermic surgical procedures (Agarwal, 1995). Plasmapheresis is effective because the autoantibodies, which are most often IgM, are loosely bound to the erythrocytes, and IgM antibodies are incapable of diffusing into the extravascular space (Teachey, 2005). The specifics of each exchange (ie, volume, frequency, duration) must be individualized, planned by an appropriate consultant, and monitored closely.



• When CAD is secondary, as in infectious disease or lymphoma, treatment is directed at avoidance of cold along with appropriate treatment of the underlying malignancy.



• CAD is so uncommon in children that no specific recommendations for therapy are available.



• In patients who are pregnant, avoid all cytotoxic therapy or immunosuppressive therapy other than glucocorticoids because of the potential teratogenic effects on the fetus and the long-term effects on the mother.



• Rituximab, anti-CD20 antibody, has been administered to patients with CAD with prompt response in case studies. One case series suggested higher response rates than were previously achieved with alkylators, glucocorticoids, or purine nucleoside analogs (Webster, 2004; Gertz, 2006).



• IVIG was used successfully in an infant with IgA-associated autoimmune hemolytic anemia (Hoppe, 2004).

Surgical Care

Splenectomy is usually ineffective because the liver is the predominant site of sequestration. However, if the patient has splenomegaly, then the disease may respond to splenectomy. More importantly, a lymphoma localized to the spleen may only be found after splenectomy.

• Ischemic necrosis of fingertips or nose may require plastic repair.



• Ambient operating room temperatures usually result in cooling of the patient and require close attention.



• Critical planning is needed if a patient with a high titer, high thermal amplitude cold agglutinin requires cooling for cardiovascular surgery. These patients may require monitoring of core body temperatures to avoid cooling to temperatures at which the cold agglutinin is still active. Preoperative preparation of the patient by reducing the titer of the cold agglutinin to reduce its effective thermal amplitude may be needed.



• In patients requiring bypass surgery, a high titer of cold agglutinin is reduced by a combination of plasmapheresis and hemodilution achieved by standard techniques used in open heart surgery.



• In general, transfusions should be avoided and should be reserved for patients with symptomatic anemia or a rapidly falling hematocrit value. Thus, most patients are unlikely to require a blood transfusion.
  
  
  • Typing and cross-matching may be very difficult because of clumping of the RBCs at room temperature when dealing with a high thermal amplitude cold agglutinin. Therefore, all cross-matching (compatibility testing) should be performed at 37°C with the use of IgG-specific antiglobulin reagents to avoid misleading results due to the cold agglutinin in the serum and the RBC-bound C3d.
  
  
  
  • Washed (removes complement), warmed RBCs may be transfused for cardiovascular indications (ie, heart failure) or ischemic conditions in any part of the body requiring increased oxygen carrying capacity. Also, prescribe bed rest and oxygen therapy.
  
  
  
  • Transfusions should be attempted with caution, starting with a slow rate of infusion initially and discontinuing the procedure if a significant reaction is imminent. An in-line blood warmer is useful, as is performing the entire transfusion at 37°C whenever feasible. 
  
  
  
  • Transfused red blood cells may have increased susceptibility to lysis by cold agglutinins, in comparison to autologous red blood cells, because they lack proteolytically cleaved complement on their surface. This may inhibit complement-mediated lysis (Inaba, 2005).
     
• Organs that are used for transplantation (eg, kidneys) are usually kept cool with cold perfusate to preserve organ function. However, if patients with CAD require transplants, the organs may require perfusion with warm solutions prior to transplant to prevent cold-induced damage by the cold agglutinin present in the recipient.

Consultations

A hematologist-oncologist working in collaboration with a blood banker is helpful in complicated cases.

Diet

Patients should include good sources of folic acid, such as fresh fruits and vegetables, in their diet.

Activity

Activities should be less strenuous compared to those for healthy people, particularly for patients with anemia. Jogging in the cold could be very hazardous because of the added windchill factor.

Folic acid supplementation is advisable to meet increased requirements of increased RBC production due to hemolytic anemia.

Immunosuppressive and immunomodulating drugs are seldom necessary; however, in cases with underlying malignancies, they are required to treat the malignancy. Potent immunosuppression to reduce the production of monoclonal antibody and to reduce/eliminate abnormal lymphocyte clone has been achieved with cyclophosphamide (1200 mg) and vincristine (2 mg) administered intravenously on day 1 and prednisone (80 mg/d) administered orally for 5 days, with some beneficial effect in an anecdotal case. The same patient was treated 10 months later with fludarabine (25 mg/m²) daily for 5 days intravenously and then every 28 days for 3 courses. Following a third course of treatment, this patient went into remission that lasted at least 4 years (Jacobs, 1996).

Bear in mind that one uncommon reported adverse effect of fludarabine is the appearance of a warm autoantibody–induced autoimmune hemolytic anemia. However, according to the authors' experience, persons with Coombs-positive hemolytic anemias have been treated effectively with fludarabine. Responses to interferon alfa therapy have been reported. This therapy may be useful for some B-cell neoplasms (O'Connor, 1989).

Chlorambucil has also been used to treat CAD (Hippe, 1970). Corticosteroids alone may not be routinely useful in all patients with CAD, although occasionally a patient may respond. Patients with mixed cold and warm immune hemolytic anemia are more likely to respond because of the warm antibody component.

In general, use of chemotherapeutic agents, which have long-term consequences for the patient and are associated with secondary malignancies such as leukemias that are hard to treat, requires very careful decision making in collaboration with a well-informed patient. They should be used only for life-threatening, severely symptomatic disease. Therapy also may need to be administered intermittently or infrequently as the case demands. Tailor therapy to individual needs. Only currently used drugs are discussed. These will change as newer drugs become available for use.

Although alkylating agents have been used in the past and references to these treatments are part of standard texts, the authors suggest that these drugs not be used in patients with CAD because of the potential for long-term adverse effects of therapy for an essentially benign disorder.

The reader is advised to read the package insert approved by the US Food and Drug Administration before using any of the agents listed.

Drug Category: Immunosuppressive alkylating agents

Metabolites cross-link DNA, thereby interfering with cell proliferation. Not needed in patients with idiopathic CAD.

Drug Name	Cyclophosphamide (Cytoxan)
Description	Chemically related to nitrogen mustards. As an alkylating agent, the mechanism of action of the active metabolites may involve cross-linking of DNA, which may interfere with growth of normal and neoplastic cells. Cystitis can develop with long-term administration; leukemogenic potential should be kept in mind. Primary (idiopathic) form of disease is unlikely to require use of this class of drugs.
Adult Dose	Dose should be determined based on the combination regimen used to treat the underlying malignancy when CAD is secondary to an underlying malignancy
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; severely depressed bone marrow function
Interactions	Allopurinol may enhance myelosuppressive effects; may reduce digoxin serum levels and antimicrobial effects of quinolones; coadministration with high doses of phenobarbital may increase leukopenic activity; thiazide diuretics may prolong cyclophosphamide-induced leukopenia; coadministration with succinylcholine may increase neuromuscular blockade by inhibiting cholinesterase activity
Pregnancy	D - Unsafe in pregnancy
Precautions	Monitor for hematopoietic suppression with regular examination of hematologic profile (particularly neutrophils and platelets); regularly examine urine for RBCs, which may precede hemorrhagic cystitis During chemotherapy, encourage patients to empty bladder at night before bedtime and to drink plenty of water to maintain good diuresis

Drug Category: Glucocorticoids

Used for immunosuppressant properties.

Drug Name	Prednisone (Deltasone)
Description	Immunosuppressant for treatment of autoimmune or lymphoproliferative disorders. Modulates lymphocytes and decreases antibody production. Frequently used with alkylating agents.
Adult Dose	60-80 mg/d (up to 1-2 mg/kg/d) as starting dose; used for suppression of antibody production; taper dosages after several weeks, with close monitoring of adverse effects; determine dosing regimen based on multidrug regimen chosen to treat specific underlying malignancy
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; viral infection, peptic ulcer disease, hepatic dysfunction, connective tissue infections, and fungal or tubercular skin infections; GI disease
Interactions	Coadministration with estrogens may decrease clearance; concurrent use with digoxin may cause digitalis toxicity secondary to hypokalemia; phenobarbital, phenytoin, and rifampin may increase metabolism of glucocorticoids (consider increasing maintenance dose); monitor for hypokalemia with coadministration of diuretics
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Abrupt discontinuation of glucocorticoids may cause adrenal crisis; hyperglycemia (potential contraindication, assess each patient carefully), edema, osteonecrosis, myopathy, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, myasthenia gravis, growth suppression, and infections may occur with glucocorticoid use; sleep deprivation/alteration in sleep cycle common; check potassium levels and advise patients to eat plenty of fruits and vegetables to obtain adequate potassium; weight gain due to stimulation of appetite is possibly a serious issue (advise patients of this possibility); watch for development of depression; occasionally, mania or altered sleep cycle may occur; muscle weakness and wasting may become a serious problem; hypertension can be exacerbated by steroids

Drug Category: Interferons

Variable success with these agents in cold agglutinin–induced hemolytic anemia. Expense and serious adverse effects are issues to consider up front before choosing this class of drug. Used in the treatment of lymphoproliferative disorders.

Drug Name	Interferon alfa-2b (Intron-A)
Description	Identifying proper drug for use in a patient depends on patient characteristics and patient participation in decision-making process. No guarantees of success can be given with any therapy in CAD. Interferon alfa is manufactured by recombinant DNA technology. Mechanism of effect is not clearly understood. However, direct antiproliferative effects against many different kinds of malignant cells have been shown in clinical disease states (eg, lymphoma, melanoma, CGL) and modulation of host immune response may play important roles.
Adult Dose	3-5 million U/m2 SC 3 times/wk; tailor dosage as tolerated based on adverse effects (dosage has been used in lymphoproliferative disorders)
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity (anaphylactic sensitivity to mouse immunoglobulin (IgG), egg protein, or neomycin); autoimmune hepatitis, presence of severe depression
Interactions	Potential risk of renal failure when administered concurrently with interleukin-2; theophylline may increase toxicity by reducing clearance; cimetidine may increase antitumor effects; zidovudine and vinblastine may increase toxicity
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Depression and suicidal ideation may be adverse effects, but drug sometimes may be tolerated by patients with depression (decide on an individual basis); prior to initiation of therapy, perform CBC count for platelets, Hb/Hct, and WBC with differential; monitor periodically during treatment to determine response to treatment; monitor for hypothyroidism; past history of severe depression may warrant caution because of risk of recurrence; caution in cardiac arrhythmias

Drug Category: Vitamin, Water Soluble

Necessary for hematopoiesis.

Drug Name	Folic acid (Folvite)
Description	Important cofactor for enzymes used in production of RBCs. Chronic hemolytic process requires additional folate.
Adult Dose	1 mg PO qd; up to 5 mg PO qd depending on frequency and aggressiveness of hemolysis
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity
Interactions	Increase in seizure frequency and subtherapeutic levels of phenytoin reported when used concurrently
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Benzyl alcohol may be contained in some products as a preservative (associated with fatal gasping syndrome in premature infants); resistance to treatment may occur in patients with alcoholism and deficiencies of other vitamins

Drug Category: Immunosuppressant Agent

Agents in this class include antibody directed against the CD20 antigen found on surface of B-lymphocytes.

Drug Name	Rituximab (Rituxan)
Description	Effective lowering of IgM and IgG levels is achievable with this anti–B cell antibody. Hypersensitivity reactions can be severe; users of the drug should become completely familiar with the adverse reactions known to occur.
Adult Dose	375 mg/m2 IV qwk for 4 doses (days 1, 8, 15, 22)
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; IgE-mediated reaction to murine proteins
Interactions	Coadministration with cisplatin is known to cause severe renal toxicity including acute renal failure; may interfere with immune response to live virus vaccine (MMR) and reduce efficacy (do not administer within 3 months of vaccine)
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Use with caution in patients with dormant infections such as hepatitis B, hepatitis C, or CMV due to risk of reactivation; hypotension, bronchospasm, and angioedema may occur, premedication with acetaminophen and diphenhydramine may decrease incidence; discontinue treatment if life-threatening cardiac arrhythmias occur; must administer by slow IV infusion, do not administer IV push or bolus

Further Inpatient Care

• Transfusions should be used only for symptomatic anemia or acute life-threatening drop in hemoglobin or hematocrit values.

Further Outpatient Care

• Provide follow-up care after in-hospital therapy. Long-term follow-up care, with or without therapy, is important to monitor for the development of any additional illnesses, such as a lymphoproliferative disorder, that would require specific therapy.
• Provide patients with CAD with periodic follow-up care to monitor for signs of worsening or improvement that might prompt changes in management. The frequency of reassessment varies with the severity of the disease. Periodic checkups might vary from daily to weekly or monthly and eventually as infrequently as every 2-3 months. Make reevaluations more often in colder weather than in warmer weather.
• Unless a clear-cut need exists, limit the use of medications in persons with CAD.
• Monitor blood cell counts and observe for infection, renal function, development of lymphoma, and evidence of ischemia.
• Avoid exposing patients to cold, as can occur with patients waiting to undergo operative procedures. Avoid cooling blankets for any reason.

In/Out Patient Meds

• Folic acid 1 mg PO qd

Transfer

• If an institution is unable to handle the needs of a patient with a high titer, high thermal amplitude cold agglutinin hemolytic anemia who requires open heart surgery, which is usually performed under hypothermic conditions, and monitoring of thermal amplitude and core body temperature, transfer is necessary. Consultation with a hematologist and the support of a blood bank are also required.
• An alternative that may be used to induce cardiac arrest during cardiac surgery is continuous perfusion with normothermic, hyperkalemic blood during the cross-clamp period (Aoki, 1993). Such precautions must be taken in order to avoid hemolysis, renal failure, and myocardial damage in patients with CAD (Robinson, 2002).

Deterrence/Prevention

• Protective measures include avoidance of cold by covering the hands, feet, and, if possible, the face in cold weather or low windchill temperatures. An exact temperature cannot be defined because symptoms are due to the thermal amplitude and other characteristics of the antibody. In some individuals, a windchill temperature of 15°C, if sustained, precipitates symptoms; more commonly, a lower temperature of 10°C would precipitate symptoms. Sleeping uncovered may result in symptoms when the room temperature is 21°C.
• Recommendations to move to a warm climate have merit in more severe cases in which symptoms and hemolysis are less likely to develop at higher ambient temperatures.
• Avoidance of cold temperatures and adequate protection of all body parts from the cold helps to prevent the development of hemolysis.
• Idiopathic CAD itself cannot be prevented.
• The use of a cooling blanket may precipitate gangrene in rare cases.

Complications

• Brisk hemolysis due to cold exposure
• Ischemic complications at exposed sites due to prolonged cold exposure
• Other symptoms related to severe anemia
• Infrequently, development of malignant disease during follow-up care of a patient with idiopathic chronic CAD

Prognosis

• CAD may be associated with an excellent long-term prognosis if it is secondary to M pneumonia or viral infections that are, in themselves, self-limited.
• Patients with the mildly to moderately severe idiopathic or primary variety of CAD are expected to have a good long-term prognosis if excessive exposure to cold is avoided and with close medical surveillance for complications or progression to lymphoma.
• The nature of the antigenic specificity of the cold agglutinin, as when it is directed against the Pr system, may be associated with greater severity of disease.
• CAD associated with HIV infection may have a relatively poor prognosis due to the nature of the underlying disease.
• The same applies for lymphoma, with prognosis dependent on remission of the underlying lymphoma.

Patient Education

• Educating patients about the importance of keeping all body parts warm at all times and avoiding cooling of body parts is essential in a chronic disorder. Appropriate clothing is necessary in cold environments.
• Patients must comprehend the importance of daily intake of folic acid to supply a needed hematinic. Folic acid could easily become a rate-limiting hematinic in a patient with a chronic hemolytic process.
• Long-term follow-up care and vigilance for the development of systemic symptoms of any lymphoproliferative disorder are necessary because patients may become dejected about a chronic process.
• Avoidance of cold foods and working in cold storages is also important.
• For excellent patient education resources, visit eMedicine's Bacterial and Viral Infections Center and Sexually Transmitted Diseases Center. Also, see eMedicine's patient education articles Mononucleosis and Syphilis.

Medical/Legal Pitfalls

• Ensure proper handling of specimens when looking for cold agglutinins, ie, keeping the blood warm until it is tested. Blood specimens are commonly placed in a laboratory refrigerator until they are tested. This practice must be avoided when testing for cold agglutinins.
• Typing and cross-matching should be performed with blood at 37°C to avoid inaccurate test results due to nonspecific agglutination in the cold.
• Perform IgG and complement Coombs tests to detect the presence of complement on the RBCs.
• Chemotherapeutic agents should be used only for serious complications, following a discussion with the patient and consultant regarding potential risks.
• Postinfectious anemia, infectious mononucleosis, M pneumoniae infection, acrocyanosis, or cold-precipitated symptoms are clues that require follow-up care.
• Careful planning and coordination with multiple personnel are needed if patients are to undergo a procedure during which their body temperature could fall.

Special Concerns

• Preparative management of a patient for open-heart surgery requires reduction in the titer of the cold agglutinin so that the thermal amplitude is not high. This can be achieved with plasmapheresis, as discussed in Treatment. The laboratory could help to assess the temperature range of activity of the cold agglutinin after the titer has been reduced so that a minimum target temperature may be estimated. Core body temperatures may require close monitoring.



• When cold-induced autoimmune hemolytic anemia occurs in pregnant women, the pregnancy may be continued with frequent blood transfusions. Transfusions may be continued until the 37^th week, when fetal lungs have matured. Mode of delivery is not affected by the anemia and should be defined by obstetric indications. Ironically, these women are still subject to thrombophlebitis of pregnancy (Batalias, 2006).