A Primer on Myasthenia Gravis in Dogs

Myasthenia gravis is a disease of the nervous system that occurs in dogs and (rarely) cats.

Myasthenia gravis in dogs can be present at birth (ie, congenital), but is usually acquired in adult dogs. 

The most commonly affected breeds include German Shepherd dogs and Retrievers.  The most common cause of myasthenia gravis in dogs is an autoimmune condition in which antibodies in the blood attack receptors for a chemical called acetylcholine, which transmits nervous impulses to the muscles.

A Primer on Myasthenia Gravis in Dogs

What does it look like

Dogs affected with myasthenia gravis typically show up with:

  • stiffness
  • shaking
  • and weakness after exercise

The signs usually go away with rest.  The muscles in the head and throat may also be affected, leading to a slack appearance in the face and difficulty swallowing.  Some dogs will spit up their food and may even aspirate some into the windpipe, which can cause pneumonia.

How is it diagnosed

Diagnosis is based on signs of illness and several clinical tests.  Your veterinarian may give your dog a shot of a chemical similar to acetylcholine, to see if signs resolve.  A positive response to this test is suggestive of myasthenia gravis, but a definite diagnosis of the acquired disease involves checking for specific antibodies in the blood.  The diagnosis of congenital cases requires a muscle biopsy.

How is it treated

Treatment involves daily administration of drugs that replace the missing acetylcholine.

Your vet may also prescribe high doses of corticosteroids to suppress the autoimmune response.  Prognosis is generally good, with many cases clearing up on their own.  Dogs that develop pneumonia do not tend to do as well.

Related articles:
Symptoms to Watch for in Your Dog: Shaking/Trembling

Further reading:
Myasthenia Gravis in Dogs

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