Immune-mediated haemolytic anaemia: when blood is thinner than water

Immune-mediated haemolytic anaemia is a significant cause of morbidity and mortality in dogs and, although less common, can also occur in cats. Immune-mediated haemolytic anaemia can be classified as spontaneous (non-associative) when no underlying cause is identified, or disease-associated (associative) when triggered by infections, neoplasia, drugs, vaccines or inflammatory conditions. Diagnosis relies on identifying regenerative anaemia, spherocytosis and positive saline agglutination or Coomb's tests. Treatment involves immunosuppressive therapy, with corticosteroids as the first-line agent and additional immunosuppressants if there is a poor response. Blood transfusions may be required in severe cases, and thromboprophylaxis is recommended because of the risk of thromboembolism. The prognosis varies, with survival rates between 50% and 88% in dogs and approximately 77% in cats, though relapses are common. This article reviews the diagnosis, classification, treatment and prognosis of immune-mediated haemolytic anaemia in cats and dogs, incorporating recent research and consensus recommendations.