What is myasthenia gravis in dogs?
Myasthenia gravis is a disease in which the signal from the nerve no longer gets through properly to the muscle. Normally the nerve releases a chemical messenger (acetylcholine), which binds to receptors on the muscle and makes it contract. In acquired myasthenia, the immune system produces antibodies against these receptors. Too few working receptors are left, and the muscle tires quickly with exercise.
The disease mainly affects adult dogs. A study of 1,154 dogs found the highest risk in the Akita, in terrier breeds (including the Scottish Terrier), in the German Shorthaired Pointer and in the Chihuahua. German Shepherds, Golden Retrievers and Labradors are also commonly affected. Dogs under 1 year old had a lower risk. Signs that appear in puppies a few months old raise the suspicion of a rare congenital form, which has a different cause.
What are the signs of myasthenia gravis?
The typical sign is weakness brought on by exercise that eases with rest. The dog sets off normally on a walk, then after a few steps or a few minutes starts to walk stiffly or shakily, sits or lies down, and after a break can walk again. The weakness may be more obvious in the hind legs.
Other common signs:
- Regurgitation. Food or water comes back up through the mouth without the effort of vomiting, sometimes soon after a meal, sometimes hours later. The cause is megaoesophagus: the oesophagus loses its tone, widens and no longer pushes food down to the stomach.
- Weakness of the face and throat. Incomplete blinking, a dropped jaw, difficulty swallowing, a change in the bark.
- Coughing, fast breathing, fever. These can point to aspiration pneumonia, meaning food or liquid has been breathed into the lungs.
What forms does the disease take?
| Form | What it looks like |
|---|---|
| Generalised | Weakness of the legs on exercise, often with megaoesophagus. This is the most common form. |
| Focal | No obvious weakness of the legs; only the muscles of the face, the throat or the oesophagus are affected. The dog may only regurgitate. |
| Acute fulminating | Severe weakness that comes on suddenly, with floppy paralysis and megaoesophagus, which can affect breathing. It is rare and very serious. |
The focal form is easily missed: a dog that only regurgitates may be treated for a long time for a digestive problem. That is why, in an adult dog with megaoesophagus and no clear cause, the test for myasthenia is part of the work-up.
Why is aspiration pneumonia dangerous?
Aspiration pneumonia is the main serious complication of myasthenia and the most common cause of death. When the widened oesophagus holds on to food, it can be breathed into the lungs. In the 2025 series of 167 dogs, 84% had megaoesophagus or a weak oesophagus, 55% developed aspiration pneumonia, and pneumonia was the cause of 52% of deaths and euthanasias. In an older study of 25 dogs, almost half died or were put to sleep because of it shortly after being admitted to hospital.
How is myasthenia gravis diagnosed?
The diagnosis is confirmed with the acetylcholine receptor antibody test, done on a blood sample. A value above 0.6 nmol/L confirms acquired myasthenia in a dog. The sample is sent to a specialist laboratory, so the result is not available straight away.
Alongside the test, your vet may recommend:
- a neurological examination, which shows the pattern of the weakness and rules out other diseases of the nerves and muscles;
- chest X-rays, to look for megaoesophagus, pneumonia and a possible tumour of the thymus (thymoma), which is seen mainly in older dogs with myasthenia;
- blood tests, including for hormonal diseases, which can occur alongside myasthenia;
- in unclear cases, electrophysiological tests at centres with the right equipment.
A negative test does not completely rule out the disease. In a series of 167 dogs published in 2025, about one in five (22%) had signs of myasthenia but antibody levels below the cut-off. In these dogs the diagnosis rests on the other tests and on the response to treatment.
A neurological consultation tells you where the problem comes from and what to do next.
How is myasthenia gravis treated in dogs?
Treatment has two parts: medicines that improve transmission between nerve and muscle, and measures that prevent pneumonia. The main medicines are anticholinesterases, which give acetylcholine more time to act; in some dogs the vet adds medicines that regulate the immune system. The choice of medicine and the dose are decided by the vet, and adjustments are made based on the check-ups.
At home, feeding matters most:
- feeding in an upright position, with the dog raised up on his hind legs or sitting in a special chair, and keeping him upright for a few minutes after the meal;
- the consistency of the food and the number of meals agreed with your vet, according to what your dog tolerates;
- in severe cases, a feeding tube placed directly into the stomach for a while.
Exercise is measured out: short walks, stopping before tiredness sets in.
What is the outlook for a dog with myasthenia gravis?
The outlook is generally good for dogs without pneumonia and more guarded for those with complications. Many dogs go into remission:
- In a 2001 study of 53 dogs treated without immunosuppression, 47 went into clinical and immunological remission after an average of 6.4 months. All 6 dogs that did not go into remission had a tumour.
- In a 2021 study of 94 dogs, complete clinical remission (no signs for at least 4 weeks after treatment was stopped) occurred in 31% of them, and a further 15% had no signs while they were on treatment. Remission was less common in older dogs, in dogs that regurgitated and in dogs with high antibody levels at the start.
- In the 2025 series of 167 dogs, complete and lasting remission occurred in 18%, after a median of almost 2 years. Dogs whose oesophagus was affected had shorter survival.
The differences between the studies come down to the populations studied and how remission was defined. In practical terms: many dogs can lead a good life, some can come off treatment after a few months, and others need it long term. Repeating the antibody test shows whether the disease is dying down. Treatment is never stopped without your vet's agreement.
If you notice unusual tiredness on exercise or regurgitation in your dog, a neurological consultation will establish whether the pattern fits a neuromuscular disease. For other signs, see the guide to neurological symptoms in dogs, and if you live in another town, read the information for patients from outside Cluj.
A neurological consultation tells you where the problem comes from and what to do next.
Frequently asked questions
Can myasthenia gravis in dogs be cured?
In many dogs the disease goes into remission: the signs disappear and the antibodies fall back to normal levels, sometimes to the point where treatment is no longer needed. Remission is less likely in older dogs, in dogs that regurgitate and in dogs with an associated tumour. Only your vet can decide, based on the check-ups, whether the treatment can be reduced.
Can a dog with myasthenia go for walks?
Yes, but short ones, adapted to him. Walks stop before he gets tired, with frequent breaks, and exercise is increased only once your vet confirms the disease is under control.
Is myasthenia gravis inherited?
The acquired form, which is the most common, is autoimmune and is not passed on like a simple genetic disease, although some breeds are more prone to it. There are also rare congenital forms, which appear in puppies a few months old and have a different cause.
What should I do if the treatment no longer seems to be working?
Phone your vet the same day. Worsening weakness can mean the disease is not under control, but it can also be a side effect of the medication or pneumonia. Do not change the doses yourself.
Sources
- MSD Veterinary Manual (professional), Inflammatory Disorders of the Peripheral Nerve and Neuromuscular Junction: myasthenia gravis
- MSD Veterinary Manual (Dog Owners), Disorders of the Peripheral Nerves and Neuromuscular Junction in Dogs
- Shelton GD et al. 1997, Risk factors for acquired myasthenia gravis in dogs: 1,154 cases, JAVMA
- Dewey CW et al. 1997, Clinical forms of acquired myasthenia gravis in dogs: 25 cases, Journal of Veterinary Internal Medicine
- Shelton GD, Lindstrom JM 2001, Spontaneous remission in canine myasthenia gravis, Neurology
- Dos Santos RX et al. 2025, Case series of canine myasthenia gravis: a classification approach with consideration of seronegative dogs, Journal of Veterinary Internal Medicine
- Forgash JT et al. 2021, Clinical features and outcome of acquired myasthenia gravis in 94 dogs, Journal of Veterinary Internal Medicine
This article is for information only and does not replace a veterinary consultation.