Australian Shepherd Health & Genetics Institute

Australian Shepherd Health & Genetics Institute

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Myasthenia Gravis


What is myasthenia gravis (MG)?

Myasthenia gravis is an autoimmune disease that targets the motor end plates, the connection between the nerves and the voluntary muscles.   Affected dogs often also have megaesophagus, an enlargement of the esophagus which interferes with the passage of food to the stomach.  The disease can arise at any time after a year of age, with most being diagnosed between 2 and 4 or from 9 to 13 years.  In the older dogs the disease may be acquired, but is more likely to be inherited.

 How do I know if my dog has MG?

Dogs with MG tire easily and may stumble for no apparent reason; vigorous exercise may bring on collapse.  Severe attacks can mimic toxic exposure. The disease can be diagnosed with a blood test though other tests may be run first to rule out other possible causes of symptoms.

 What does having MG mean for my dog?

MG cannot be cured and requires treatment.  Dogs receive drugs that improve motor nerve cell communication.  Prognosis in treated dogs is good though it is necessary to guard against aspiration pneumonia in dogs which have secondary megaesophagus.

 How common is MG in Aussies?

It is very rare.  However, it is important to keep in mind that breeders should approach all chronic autoimmune disease as a single health concern; different types of autoimmune disease frequently occur in affected families.

 Is MG inherited?

Yes, with the possible exception of some late-onset (9+ years) cases.  Autoimmune diseases are genetically predisposed:  The dog must have the genes to get the disease, but not every dog with the genes will become ill.

 Is there a screening or DNA test MG?

Not at this time.

 What does MG mean for my breeding program?

Breeders should approach each autoimmune disease as part of an overall health and breeding issue because different autoimmune diseases frequently occur in an affected family.  See Autoimmune Disease & Breeding.