A case of warm autoimmune haemolytic anaemia with intravascular haemolysis: a rare presentation

Autoimmune haemolytic anaemia (AIHA) is a rare (prevalence 0.2 -1.0 per 100,000 population) but a potentially fatal condition. Diagnosis of AIHA is based mainly on Direct Agglutination Test (DAT/Coomb's test). AIHA is classified into warm (optimal autoantibody reactivity at 37°C) and cold (optimal autoantibody reactivity at 4°C) types. Based on the presence or absence of an underlying cause, it is divided into primary (idiopathic) and secondary (secondary to lympho proliferative disorders, autoimmune disease, drugs and non-haematological malignancies). Warm type accounts for about 70% of cases with AIHA. It can occur at any age, but mostly after 40 years. Haemolysis in warm AIHA is mediated by IgG alone or IgG with complement. Once immunoglobulins are bound, the red cells are taken up by the macrophages of the reticulo-endothelial system which has receptors for the Fc fragments of the immunoglobulins. As the red cells are haemolysed extravascularly this occurs mainly in the spleen. Intravascular haemolysis is unusual in warm AIHA, although it can occur rarely, as warm autoantibodies can fix complements. We report severe warm AIHA in an adult with evidence of intravascular haemolysis, which is an unusual presentation.