What is Myasthenia Gravis in Dogs?


Myasthenia gravis in dogs is a relatively rare neuromuscular disease
in which there is a breakdown in the transmission of signals between nerves and
muscles. Dogs with myasthenia gravis exhibit extreme weakness and excessive
fatigue. The condition keeps muscles from contracting, causing affected
dogs to become weak; severe weakness is the primary symptom of myasthenia
gravis in dogs.

Certain dog breeds are predisposed to a congenital (inherited)
form of myasthenia gravis, including English Springer Spaniels, Jack Russell
Terriers, Smooth Fox Terriers and Smooth-haired Miniature Dachshunds. However,
most cases are acquired and not inherited, so all puppies and dogs are at risk.

In most cases, myasthenia gravis is an acquired problem in adult dogs. It is thought to be the result of a defect in the dog’s immune system that causes antibodies to mistake the dog’s muscle receptors as the enemy – essentially attacking them and preventing them from working properly. This keeps the muscles from contracting, causing affected dogs to become weak. Female and male dogs are equally at risk.

Miniature Smooth Haired Dachshund.
iStock / Getty Images Plus/ NORRIE3699

“For some reason, we often see peaks of acquired myasthenia gravis in dogs between the ages of two and four, and then again from nine to 13 years of age. Unfortunately, pet parents may think it is just the signs of aging of their senior dog, and not seek out proper diagnosis, management and treatment,” says W. Jean Dodds, DVM, and founder of Hemopet, the first non-profit national animal bloodbank.

Puppies
with congenital myasthenia gravis are typically diagnosed at six to eight weeks
of age.

The symptoms of myasthenia gravis in dogs are progressive and
can vary greatly from dog to dog. The most common symptom
is muscle weakness that worsens with exercise, but improves with rest.

Megaesophagus: A Common Result of Myasthenia Gravis in Dogs

Often the esophagus is affected in dogs with myasthenia gravis; these dogs have trouble swallowing and drinking. When a dog’s esophagus loses its motility due to myasthenia gravis, secondary megaesophagus can occur. Megaesophagus is when the esophageal muscle relaxes so that food and liquids cannot be pushed down into the stomach by normal muscle contraction. In some situations, this condition may cause the dog to aspirate food and water, which can in turn result in aspiration pneumonia.

Smooth Fox Terrier
iStock / Getty Images Plus/ derevetskaira

Because megaesophagus can cause aspiration pneumonia, it is a
dangerous symptom. Feeding dogs with megaesophagus can be done safely, but it requires
some extra effort. Make
sure that your dog’s head is elevated during feeding (and for 10 to 15 minutes
afterward). Your veterinarian will work with you in finding the best way to
make sure your dog can eat and drink without the risk of regurgitation or
aspirating food/water.

Diagnosis of Myasthenia Gravis in Dogs

If your dog suffers from muscle weakness, alert your veterinarian at once. The vet will perform a complete physical exam and recommend the best choice of diagnostic testing.

If necessary, your dog will receive treatment specific to his
needs. These may include the use of anticholinesterase drugs, which help to improve muscle strength
by reducing the attack by antibodies on the dog’s muscle receptors.

Unfortunately, there is no
prevention or cure for this disease. Treatment and careful at-home care can
help dogs with myasthenia gravis maintain a quality of life for a reasonably
long time. The more attention paid to the prevention of aspiration pneumonia,
the better the prognosis for your dog.

“Myasthenia
Gravis does demand patience and commitment from the pet caregiver,” emphasizes
Dr. Dodds. “Remember, it is a progressive condition that does not have a cure,
but we can try to slow the progression and side effects with the right
supportive care and medications for a longer, quality life.”



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