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IMHA (Immune Mediated Haemolytic Anaemia) Fact Sheet

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IMHA is a disease where the body’s immune system destroys its own red blood cells. This often leads to severe anaemia and poor oxygen delivery to multiple organs such as the kidneys, liver, brain, etc. Both dogs and cats are affected by this condition.


The signs that a patient shows vary depending on the severity of the disease. Some dogs and cats suffer acute severe disease and can present collapsed and unable to stand. Their gums are often very pale and you may also notice a yellow tinge in their eyes, mouth or skin. This is due to staining of the mucous membranes or skin with bilirubin which gets released into the circulation when large numbers of red blood cells are destroyed. The patient may be breathing fast due to the anaemia or the formation of blood clots in the lungs, which is common in cases of IMHA in dogs and cats. Sometimes the disease is not as severe and the signs may be milder.


IMHA in dogs and cats can be triggered by different factors including infectious organisms, tumours and even drugs. It is therefore extremely important to inform your vet of any medication that your pet has recently received. Other tests will then be carried out to make sure that there is not an underlying disease present. When a cause is not found the disease is designated idiopathic or primary IMHA; this means that without an obvious case, your pet’s immune system has started destroying its own red blood cells.


A diagnosis of IMHA in dogs and cats can often be made based on the clinical signs, blood tests and examination of a blood smear. Other tests should then be performed to differentiate primary IMHA from that triggered by other diseases (tumours, infections, etc). This is extremely important as the treatment of these conditions is very different from that of primary IMHA. An incorrect diagnosis will lead to poor treatment response and even death. Additional tests which may be carried out include X-rays, abdominal ultrasound, serological tests to check for infectious organisms and, occasionally, bone marrow biopsies.


If an underlying disease is present, then this should be treated. Successful treatment of the underlying disease often leads to resolution of IMHA. In cases of idiopathic or primary IMHA in dogs and cats (where a clear cause is not present), steroids are given to suppress the immune system. Other drugs such as azathioprine or ciclosporin are sometimes used in conjunction with steroids, particularly in difficult or severe cases. Some pets will require blood transfusions to replace red blood cells. This is not always effective as the transfused red blood cells may also be destroyed by the immune system. In these cases, a synthetic haemoglobin solution called Oxyglobin™ may be used. Your vet may also advise using heparin or aspirin to prevent the risk of clot formation.


The prognosis for IMHA in dogs and cats is very variable and depends on the severity of the disease and the presence of an underlying cause. In recent years, there has been some research into new drugs and massive improvement in the care and monitoring of these patients. However, despite all efforts, sadly some patients succumb to the disease. The main risk of death is within the first few days/weeks of treatment. The prognosis for dogs and cats that respond to treatment and are discharged from hospital is generally good although some may require long term treatment.


If you are concerned about the health of your pet you should contact your veterinary surgeon.

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