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Hereditary myopathy is an inherited muscle disease. This disease can occur rarely in Labrador Retrievers as a result of an insufficiency of type II muscle fibers. It can also be found rarely in Bouvier des Flandres (it was formerly known as degenerative primary polymyopathy) leading to generalized muscle weakness. In Labrador Retrievers, the weakness may be seen as early as six weeks of age. In Bouvier des Flandres, the condition won’t usually become apparent until the dog is around two years old.
Both Labrador Retrievers and Bouvier des Flandres can experience hereditary myopathy, also called centronuclear myopathy, which will lead to their experiencing muscle weakness along with other symptoms.
In Labrador Retrievers experiencing myopathy, puppies may first present with an unusual gait. By the time he is about five months old, his growth may be stunted and he may demonstrate a general weakness that comes and goes. The weakness also may be more pronounced when he is excited, exercising or when the temperature is cold. Your dog may also struggle to keep his head elevated in a typical position, which can be seen as soon as 3 months of age. Upon the condition worsening, his muscles will shrink, which will cause some of his bones to appear to stand out. The majority of dogs will still be alert. Often progression of the disease will slow or stop between 6-8 months old and your dog’s condition will not worsen; in fact, some will show a slow improvement.
In myopathy of Bouvier des Flandres, the condition will be apparent as your dog is about two years old. He will demonstrate an odd gait, generalized weakness that worsens significantly when exercising and atrophy of his muscles. Dogs often have difficulty swallowing and many have an enlarged esophagus, called megaesophagus, which will lead to his regurgitating after he eats and can cause aspiration pneumonia.
There are two types of hereditary myopathy in dogs; Labrador retriever myopathy and Bouvier des Flandres myopathy. Both diseases are rare and involve muscle weakness.
Labrador Retriever myopathy occurs through autosomal recessive inheritance. It is not clear how the disease is inherited when considering Bouvier des Flandres myopathy.
If your dog is showing signs of muscle weakness or other symptoms, it is important to have him examined by your veterinarian. An examination of your dog will be conducted and your veterinarian will ask you for information regarding the symptoms that you have noticed, when you first noticed them and any changes that you have observed. Your veterinarian may notice that your dog’s tendon reflexes are not present.
Should your Labrador Retriever be experiencing muscle weakness (usually between 6 weeks and 7 months of age), your veterinarian may measure his muscle response to electrical stimulation through electromyography and will consider taking samples of his muscles (muscle biopsy) to be evaluated by a pathologist.
In Bouvier des Flandres myopathy, your veterinarian will use electromyography or muscle biopsy to confirm the diagnosis. Should your dog have the condition, the muscle will show multifocal necrosis, hypertrophy, atrophy, increased fibrosis, and an increase in the number of fibers that have internal nuclei.
Blood tests will be conducted; in both Labrador Retriever myopathy and Bouvier des Flandres myopathy, the CK is elevated. In Labrador Retriever myopathy, it is not unusual to see the CK level be up to 30 times the normal amount.
While a cure does not exist for either condition, some of the symptoms experienced in Labrador Retriever myopathy can be minimized through certain medications (for example, diazepam). In Bouvier des Flandres myopathy there is no treatment for megaesophagus, however the condition can be managed; small frequent meals that are high in calories are recommended. When fed, the food should be provided at an elevated location, as this will allow gravity to assist the food to pass through your dog’s system. It is also recommended that you try different consistencies of food to see which leads to the least amount of regurgitating.
There is no treatment for either disease, however dogs that are not severely impacted by the condition can go on to have a good quality of life; they may just be limited in their ability to exercise and in the case of Bouvier des Flandres, may require a modification of their diet and how they consume their food. Dogs that have a severe case of the condition, may unfortunately experience significant disability.
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