Causes, Symptoms, and Treatment of Myasthenia Gravis in Dogs

Myasthenia Gravis, which can be encountered in dogs and rarely in cats, is a neuromuscular disease. Neuromuscular diseases affect muscles, nerves, or both muscles and nerves. This disease, which occurs as a result of the disruption of impulse transmission from nerves to muscles, causes weakness in dogs because it prevents muscle contraction. Certain dog breeds, including Jack Russell Terriers, English Springer Spaniels, and Miniature Dachshunds, are more affected by Myasthenia Gravis. Myasthenia gravis in dogs can be congenital or acquired. Acquired myasthenia gravis, like other immune-mediated diseases, can arise from many different causes. In this article, we will provide information about myasthenia gravis, a little-known condition whose effects should not be ignored. What is Myasthenia Gravis in Dogs? Each muscle in the body is controlled by its own nerve, but this nerve is not directly connected to the muscle. There is a small gap at the junction between the nerve and the muscle. Signals travel like an electrical current and, when they reach the nerve ending, they travel through the gap to the muscles. Under normal conditions, the gaps where the signals are transmitted to the muscles are filled by a chemical called acetylcholine. Acetylcholine is released from the nerve ending, fills the gap between the nerve and the muscle, and attaches to its receptors in the muscles. When this attachment occurs, it triggers the signals that cause the muscles to contract. In dogs with Myasthenia Gravis, messages or signals between nerves and muscles cannot be properly transmitted.

What is Myasthenia Gravis in Dogs?

Each muscle in the body is controlled by its own nerve, but this nerve does not connect directly to the muscle. There is a small gap at the junction between the nerve and the muscle. Signals travel like an electrical current and, upon reaching the nerve ending, travel through this gap to the muscles. Under normal conditions, the gaps where signals are transmitted to the muscles are filled by a chemical called Acetylcholine. Acetylcholine is released from nerve endings, fills the space between the nerve and muscle, and attaches to its receptors in the muscles. When this attachment occurs, it triggers signals that cause the muscles to contract. In dogs with Myasthenia Gravis, the messages, or signals, between nerves and muscles cannot be properly transmitted.

When this connection between nerves and muscles is not properly established, the muscles begin to weaken because they cannot respond to the messages and contract. As muscle weakness progresses, dogs have difficulty standing and performing standard exercises. This problem with signal transmission to the muscles does not only affect the limb muscles. Esophageal muscles, swallowing muscles, and respiratory muscles can also be affected.

As we mentioned earlier, Myasthenia Gravis in dogs can be congenital or acquired. The acquired form of the disease is more common. It is known that the risk of acquiring this disease later in life is higher in breeds such as Golden Retrievers, Akita Inus, and German Shepherd Dogs compared to other breeds.

What are the Causes of Myasthenia Gravis in Dogs?

The causes of Myasthenia Gravis in dogs can vary depending on whether the disease is congenital or acquired. In the case of congenital Myasthenia Gravis, the main reason is that dogs are born with very few acetylcholine receptors. When Myasthenia Gravis occurs later in life in dogs, the cause is usually an error in the immune system.

The primary function of the immune system is to protect the body against infections or foreign invaders. Antibodies are produced for this purpose. Acquired Myasthenia Gravis occurs when the body produces antibodies that attack and destroy acetylcholine chemicals. It is unfortunately unknown why the immune system in dogs suddenly attacks acetylcholine chemicals, which connect nerves and muscles, when such a structure did not exist for years. Although very rare, cancer formations can be observed in both cats and dogs following this behavior of the immune system. It is also known that insufficiently active thyroid glands and immune system diseases affecting muscles or nerves can be a cause of Myasthenia Gravis. Whatever the cause, changes in the immune system's reactions reduce the number of receptors and cause muscle weakness. Symptoms of Myasthenia Gravis in Dogs Dogs with Myasthenia Gravis usually experience weakness after exercise lasting only a few minutes. This weakness can affect all legs or only the hind legs. Muscle tremors are usually noticeable. Dogs experiencing this symptom regain their former healthy appearance after a short rest and can be active again without the exercise-induced weakness recurring. Although Myasthenia Gravis in dogs causes complaints that appear after exercise, it can also manifest itself with different symptoms.

Symptoms of Myasthenia Gravis in Dogs

Dogs with Myasthenia Gravis usually experience weakness after a few minutes of exercise. This weakness can affect all legs or only the hind legs. Muscle tremors are often noticeable. Dogs experiencing this symptom often regain their former healthy appearance after a short rest and can become active again without the exercise-induced weakness reappearing. Although Myasthenia Gravis in dogs causes complaints that appear after exercise, it can also manifest itself with different symptoms.

Symptoms such as progressive muscle weakness, sleeping with eyes open, difficulty swallowing, changes in barking sound, coughing, difficulty breathing, and excessive salivation can also occur. There may be other underlying problems causing increased salivation in dogs. You can read our article titled "Why Do Dogs Drool?" here. Among these symptoms, we want to explain the change in barking sound.

Myasthenia Gravis in dogs can affect muscle groups in different parts of the body. The voice change may be due to involvement of the esophagus, pharynx, and facial muscles. Symptoms can be mild or severe. Myasthenia gravis, or focal muscle weakness, most often results in a condition called megaesophagus. This is perhaps the most common symptom of acquired myasthenia gravis and is actually a secondary condition. In megaesophagus, the esophagus widens. When it widens, muscle tone may be lost, and it may not function properly. Food and liquids can cause blockages in the esophagus, and in dogs, it can also cause vomiting. Another important thing to know about megaesophagus is that aspiration can result in pneumonia. This condition is characterized by infection due to food and liquid filling the lungs. In addition to all this, it should be stated that some dogs with acquired myasthenia gravis have a chance of developing a type of tumor called 'thymoma' in the chest area.

Treatment of Myasthenia Gravis in Dogs

When symptoms of Myasthenia Gravis appear in dogs, it is necessary to consult a veterinarian without delay. Veterinarians listen to the patient's medical history and perform a physical examination. Based on these assessments, imaging methods and blood tests may be used. A specific blood test called the AChR antibody test can be performed to check whether the immune system is producing antibodies against acetylcholine receptors. This test will most likely provide a definitive diagnosis of myasthenia gravis in dogs. Treatment is somewhat complex. Myasthenia gravis in dogs cannot be completely cured. Unfortunately, some puppies are born with this disease and do not survive for long. However, in cases of acquired myasthenia gravis, it is possible to offer dogs a more comfortable life. Establishing effective communication with veterinarians and ensuring that the dog's daily care is not neglected is critically important during the treatment process. Various treatment options can be implemented. Drug treatments, immunosuppressive therapies, and supportive therapies are all very important. As part of the treatment for Myasthenia Gravis in dogs, veterinarians will provide comprehensive information to dog owners and explain all the important aspects to consider.

Myasthenia Gravis in dogs is incurable. Unfortunately, some puppies are born with this disease and do not survive long. However, in cases of acquired Myasthenia Gravis, it is possible to provide dogs with a more comfortable life. Effective communication with veterinarians and maintaining regular daily care are critically important during the treatment process. Various treatment options can be implemented. Drug treatments, immunosuppressive therapies, and supportive treatments are very important. Veterinarians will provide comprehensive information to dog owners regarding the treatment of Myasthenia Gravis in dogs, explaining all the important aspects to consider.