Warm reactive autoimmune haemolytic anaemias are associated with IgG antibodies to red blood cells. These antibodies react best at body temperature.
Fifty percent of cases are idiopathic. Of the known causes, the most common associations are with lymphoid neoplasms, such as chronic lymphoid leukaemia, or autoimmune disease, such as systemic lupus erythematosus.
Red cells are opsonised with either antibody alone, or antibody and complement components, and subsequently removed by splenic macrophages.
Patients may be of any age but it is most common in people over 30 years of age. Presentation is usually with jaundice and splenomegaly.
The patients red cells are direct Coombs' test positive; they promptly agglutinate when mixed with antiglobulin reagent. In 50% of cases, the red cells have both IgG and C3 fixed on their surfaces; in 40% of cases, IgG only; and in 10%, complement only.
Treatment, when required, is with steroids, initially at a high dose which is then tapered off as the response allows. In some patients, splenectomy may be required. Its benefits must, as always, be balanced against the increased risk of infection, especially from capsulated organisms such as Streptococcus pneumoniae.
Immunosuppressive drugs are rarely of value.
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