Neuromuscular diseases affect animals as well as humans, and one of the most common is known as Acquired Myasthenia Gravis. It's a disorder that interrupts communication between the nerves and the muscles. It's also an autoimmune disease, meaning it's caused by the body's own immune system turning against itself. Specifically, the immune system attacks and destroys junctions, which are places where the neurons (nerve cells) and muscles interconnect. Once these junctions are destroyed, the adjacent muscles cannot be controlled or are poorly controlled.
With myasthenia gravis, a dog will experience muscle weakness, especially in the limbs and the muscles affecting the eyes, facial expressions, throat and esophagus. Sixty percent of affected dogs will become fatigued after any significant exercise; others will develop difficulty swallowing or noticeable changes in their voice. The dog may appear only slightly affected, or else be almost entirely immobile.
Some animals also experience a complication known as megaesophagus, in which the muscles of the esophagus become flaccid and useless. Dogs with this problem vomit when they try to eat, because they cannot effectively move food down into their stomachs. This causes significant weight loss. Many dogs with megaesophagus also end up with pneumonia, as a result of inhaling food and saliva during regurgitation. The condition can be fatal very rapidly, so proper diagnosis and treatment is essential.
Mixed-breed dogs are less vulnerable to the disorder than purebreds. Animals that are less than one year old, and older males that haven't been neutered, are less likely to develop the condition. Meanwhile, breeds that are susceptible to acquired myasthenia gravis include: Akitas, Chihuahuas, Dalmatians, Doberman Pinschers, German Shorthaired Pointers, Rottweilers and all types of terriers, especially Jack Russell and Scottish terriers. In many animals, myasthenia gravis will go into remission on its own, without treatment.
A second, untreatable form of the disease is congenital and occurs when a dog is born without the normal junctions connecting the neurons and striated muscles. Congenital myasthenia gravis is passed on through recessive genes, and is prominent in the Jack Russell Terrier, Smooth Fox Terrier and Springer Spaniel breeds. Miniature Dachshunds also develop a form of the disease, however it normally resolves as the animal ages.
Myasthenia gravis is a common disease. Therefore, any dog that appears to have muscle weakness or difficulty swallowing should be tested. Diagnosis of the disorder is made through a blood test; and progress made during treatment also is measured through regular blood tests. Your dog may need to be tested for other conditions as well, since autoimmune diseases often go hand-in-hand with other medical issues, including cancer. Treatment for myasthenia gravis consists of stopping the autoimmune reaction by a combination of immunosuppressant drugs, corticosteroids and other medications. Lifestyle changes, such as feeding the dog from elevated food dishes to prevent vomiting, also will be recommended by your veterinarian. If treated carefully, dogs with this condition can for many years and experience a good quality of life.