Immune mediated haemolytic anaemia (IMHA) in dogs

Overview

• Immune mediated haemolytic anaemia (IMHA) is when the body’s immune system attacks and destroys its own red blood cells, causing life-threatening anaemia.
• Symptoms of IMHA include low energy, pale gums, breathing problems, and collapse.
• Dogs with IMHA often need intensive care and several months of medication. Sadly, due to the seriousness of the condition, survival rates are low.

What is IMHA?

Immune mediated haemolytic anaemia (IMHA) is when the immune system mistakenly attacks and destroys red blood cells, which can lead to:

• Life-threatening anaemia (lack of red blood cells) - this is extremely serious because red blood cells deliver oxygen all around the body, so it’s not possible to live without them.
• Kidney damage – due to a surge of haemoglobin (contents of red blood cells) into the bloodstream.
• Liver problems and jaundice (yellow tissues) – due to a surge of bilirubin (a red blood cell breakdown product) into the bloodstream.
• Blood clots inside the blood vessels – which prevent blood from reaching vital organs such as the brain, lungs, spleen, kidneys and liver. This is a common, and potentially life-threatening complication of IMHA.

Left untreated IMHA can quickly lead to death.

What causes IMHA?

There are two types of IMHA, primary and secondary.

Primary IMHA (60-75% of cases)

Primary IMHA is when the immune system attacks the red blood cells for no apparent reason. Certain breeds such as Cocker Spaniels, Springer Spaniels, Irish Setters, Poodles, Collies and Old English Sheepdogs are more prone to primary IMHA, so there may be a genetic element to it – however, there is no evidence to prove this yet. This is by far the most common type of IMHA, making up 60

Secondary IMHA

Some cases of IMHA are triggered by something such as an adverse drug reaction, a reaction to a blood transfusion, certain types of cancer, or sometimes (extremely rare in the UK) parasites living inside the red blood cells.

Symptoms of IMHA

Some dogs develop IMHA slowly over a few weeks, but most develop symptoms very rapidly, over a few days. Symptoms often include:

• Pale gums (white, yellow or grey)
• Low energy (lethargy)
• Reduced appetite
• Weakness and collapse
• Jaundice (yellow skin, eyes or gums)
• Fast breathing
• Racing heart rate (more tricky to spot than other symptoms)

Diagnosis and treatment

To diagnose IMHA, your vet will need to examine your dog and run some blood tests. If they are confirmed to have it, they will need intensive nursing and a variety of treatments, such as:

• Steroids and/or other immunosuppressant drugs – to stop their immune system from destroying their red blood cells, and allow their body to start replacing what has already been destroyed. It’s likely that your dog will need these medications for several months.
• Blood transfusion – if your dog is severely anaemic, they might need a blood transfusion to save their life.
• A fluid drip – to support their vital organs such as the liver and kidneys while they recover.
• Anti-clotting medication – to help prevent them from developing blood clots, which are a common and life-threatening complication.
• Oxygen – if your dog is severely anaemic, they might need to be given oxygen to help their remaining blood cells carry as much as possible around the body.
• Gastro-protectants – it may be necessary to give your dog medication to protect their guts from the high dose of steroids and other immunosuppressive (immune system controlling) drugs they are being prescribed.

If your dog has a severe case of IMHA they may need to be transferred to a specialist veterinary clinic for treatment.

Ongoing care at home

Once your dog has started to improve, they will be sent home to continue recovering. You will need to give them their medication, keep a close eye on them and make sure they continue to eat and drink.

• Medication - it’s very important you give your dog their medication at the right times. You may find our medication planner useful. Never stop your dog’s medication early, even if they seem fully recovered as this can cause serious problems. Steroids in particular can cause serious side effects if they are stopped without reducing the dose gradually, so make sure you don’t run out.  
• Food and drink - initially you may need to tempt your dog to eat by warming their food and/or hand feeding them. If your dog stops eating or drinking, contact your vet straight away.
• Bedding - your dog will need a warm, comfortable and quiet place to rest and recover.
• Exercise - it’s fine for your dog to have a little wander around the house and garden but they shouldn’t do any strenuous exercise, or be taken on long walks until they’ve fully recovered.

Check-ups and monitoring

Your dog will need regular check-ups and blood tests to ensure they are continuing to improve. Your vet will ask how they are in themselves, perform a physical exam, and run a blood count to check the amount of red blood cells they have. To begin with, your dog may need check-ups every few days, but these will decrease in frequency as their condition improves.

Outlook

Dogs that develop IMHA quickly over a few days tend to have a very poor survival rate. Dogs that develop it slowly over a few weeks tend to have a slightly better survival rate. IMHA also recurs in 11-15% of dogs, so you’ll need to keep an eye out for returning symptoms. If your dog developed IMHA due to a drug reaction it’s very important to ensure they don’t have that drug again. A note will be made in their clinical records but it’s sensible to mention it to your vet/future vets each time they are prescribed anything, and to tell anyone who looks after them.

When to contact your vet

IMHA is a very serious illness that needs intensive, emergency treatment from a vet. If your dog has pale gums, or you suspect they might be developing IMHA, contact your vet immediately for an emergency appointment. If your dog has had IMHA in the past, and is developing symptoms again, contact your vet immediately.

Cost

Treatment for IMHA can be very expensive because it requires such rapid and intensive treatment. It’s important to speak openly to your vet about your finances, the cost of treatment, as well as what you think is right for your dog. There might be more than one treatment option, so if one doesn’t work for you and your dog then your vet may be able to offer another.

Consider taking out dog insurance as soon as you bring your dog home, before any signs of illness start. This will give you peace of mind that you have some financial support if they ever become unwell.

Published: January 2023