Auto Immune Haemolytic Anaemia
Auto immune haemolytic anaemia, sometimes call primary immune mediated haemolytic anaemia is a serious condition in which the dogs own immune system attacks and destroys the red blood cells known as erythrocytes, thus accelerating their destruction and removal. This condition may occur at any age but the usual age at onset is between two and eight years old and is four times more common in bitches, compared with dogs. This condition can occur in all dog breeds and in addition to Beardies may also occur commonly in Cocker Spaniels, Old English Sheep Dogs, Poodles and Irish Setters. There are other causes of haemolytic anaemia which should be considered as well. These include infections, drugs toxins like poisons and cancerous agents. These causes need to be excluded before concluding the haemolytic anaemia is an auto immune disorder
You will recall from the page on basic genetics that there is an association with Haplotype 4 and auto immune haemolytic anaemia but there needs to be one of the possible trigger factors as well as a favourable alignment of about 40 other genes. Involved in this complex disorder.
The clinical signs appear in increasing severity starting with lethargy, weakness and depression followed by anorexia, pale mucous membranes, icterus or jaundice with a pallor, a yellow tint to the skin and eyes. Bilirubinuria is dark brown urine caused by the excess bilirubin from the damaged blood cells. A fast pulse rate with fast breathing and difficulty breathing will all result from a rapid loss of red cells leading to a severe anaemia and if untreated to death from anaemic heart failure. On further examination a large spleen may be felt as well as an enlarged liver and a heart murmur is sometimes detected. Most of the signs are due to insufficient oxygen being transported to the body organs and tissues
Tests that a vet may do to confirm the diagnosis include a full haematology screen including a blood film which helps to identify the source of the anaemia whether due to blood loss, haemolysis or abnormal breakdown, or deficiency in red cell production. A direct Coombs test uses a blood sample to detect the presence of red blood cell bound antibodies that damage the red cells without visible agglutinisation on the blood slide. Serum biochemistry may show a raised bilirubin which occurs as a result of the excessive breakdown of the red blood cells and disturbed liver enzymes. A blood count may show profound anaemia with a film showing the presence of small spherocytes, which are tiny red cells without the characteristic pallor and normally not present in a normal blood film. The red cells may appear clumped together.
Treatment is directed at preventing any further red cell destruction with the use of corticosteroids and immunosuppressant drugs. Severe anaemia can be treated with blood transfusions to maintain tissue oxygenation. Removal of the spleen may be beneficial if it is shown to be contributing to the haemolysis. The response to treatment will depend on the severity of the haemolysis. Prognosis is quite guarded due to the risk of other intercurrent infections or other complications and the mortality can be as high as 40 %. Lifelong treatment may well be required and relapses can occur.
Because of the inheritability of this condition any dogs or bitches affected should not be bred from in the future
Is all Haemolytic Anaemia Auto Immune?
Haemolytic Anaemia is NOT always an auto immune problem It can be caused by a variety of toxins, including some drugs, and by some severe infections. It is important that the vet determines the type of haemolytic anaemia the dog is suffering from.