We have a four-year old dog that has been diagnosed with myasthenia gravis. Can you provide any information on this disease, as well as make a quality of life prediction we might expect for him?
Myasthenia gravis (MG) is an uncommon neuromuscular disease that is usually acquired in adult dogs through some excessive action of the immune system. The neuromuscular junction connects motor nerves with skeletal muscle. It can be thought of as a "sparkplug gap" because a transmitter substance, stimulated by nerve impulses, travels across the gap and in turn stimulates the muscle to contract. In myasthenia gravis, the immune system attacks the neuromuscular junction directly or affects it secondarily by depositing immune complexes (antibodies and proteins) at the gap. Impulse transmission is affected and made inefficient. This leads to muscular weakness that is episodic or sustained, and typically worsened by exercise or repeated stimulation of the neuromuscular junction.
The problems may be generalized, affecting all muscle groups, or focal, affecting the muscles of breathing and swallowing. In either case the major life-threatening consequences are related to abnormal swallowing, which can lead to regurgitation and the potential for inhalation of food contents. Weight loss due to poor food intake is another important facet of the illness if associated with swallowing abnormalities.
Signs may be treated with medications that improve the efficiency of nervous impulse transmission by increasing the levels of the neurotransmitter acetylcholine. Medications may be used to suppress the immune system as well, but this can increase the risk of pneumonia. Fortunately, many MG patients will experience a spontaneous remission of their disease in weeks to four to six months, but this is unpredictable.
If patients respond to medication, the prognosis may be fair to good, with return to normal quality of life. If the swallowing disorder is present, with significant regurgitation, the prognosis is more uncertain, as this particular manifestation of the illness does not seem to respond as well to treatment. Animals with swallowing disorders will need to be fed their food and water in an elevated position. Different consistencies of food may need to be tried until the best consistency for the patient is determined. Owners must be dedicated to the proper care and management of affected dogs.
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