Clinical features

Idiopathic cold haemagglutinin disease

Cold haemagglutinin disease is mainly seen in older people and runs a chronic course. Although the condition is mostly benign, the clinical features may be very distressing and disabling. Purplish skin discoloration, maximal over the extremities (acrocyanosis), may be present in cold weather. Acrocyanosis is due to stasis in the peripheral circulation secondary to red cell agglutination. On warming the skin, the colour returns to normal or there is transient erythema. This sequence distinguishes acrocyanosis from Raynaud's syndrome. Haemolysis is usually present and the patient may be mildly icteric. Occasionally, haemolysis dominates the clinical picture, depending on the ability of the antibody to activate complement on the red cell surface. The cold agglutinins are monoclonal IgGK, but serum

Table 10.2 Serological characteristics of cold acting antibodies in the cold agglutinin syndromes.

Disorder

Specificity

Anti-I

Anti-i

Anti-P

Idiopathic (CHAD)

Mono IgMK

Mono (rare)

Secondary to:

Lymphoproliferative disease Mycoplasma pneumoniae Infectious mononucleosis

Mono IgMK/X (IgG)

Poly

Poly

Mono Poly

Paroxysmal cold haemoglobinuria

Poly

Mono, monoclonal; poly, polyclonal.

Mono, monoclonal; poly, polyclonal.

electrophoresis may not reveal a monoclonal band because the concentration of the protein is too low. Cold haemagglutinin disease may be thought of as a pre-malignant B-cell disorder, which only presents clinically because of the specificity of the antibody for red cell surface antigens.

In the laboratory, spontaneous agglutination of red cells is frequently observed, both macroscopically and on the peripheral blood film if made at room temperature (Figure 10.2). Automated blood cell counters detect the agglutinates and record erroneously high mean corpuscular volume and low Hb values, unless the sample is tested at 37°C. The DAT shows only C3d on the red cell surface; IgM cold agglutinins are not detected because they elute from the cell surface in vitro.

Cold agglutinin syndromes and lymphoproliferative disorders

Occasionally, the cold agglutinin syndrome accompanies or precedes a B-cell lymphoma or CLL. In these cases, the antibody is monoclonal and is a product of the malignant clone. The serological specificity is either anti-I or anti-i. Haemolysis is

Dat Cold Agglutinins
Figure 10.2 Cold haemagglutinin disease. Blood film showing gross haemagglutination (x20).

often more troublesome than symptoms of agglutination. The prognosis is usually that of the underlying lymphoproliferative disease.

Cold agglutinin syndromes and infections

Haemolysis due to cold agglutinins may follow infections, almost always due to M. pneumoniae, or infectious mononucleosis. Rare cases following Listeria or Toxoplasma infections have been reported. The antibodies are mostly polyclonal IgM in type but occasional IgG cold antibodies are found. The antibodies develop in response to the infecting organism and cross-react with the red cell antigens. Haemolysis appears 2-3 weeks after the infection and is usually mild and self-limiting. Occasionally, very severe and even fatal acute intravascular haemolysis develops after M. pneumoniae infection. Blood transfusion through a blood warmer may be urgently required.

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