Muscular Dystrophy (Hereditary Myopathies)
Muscular dystrophy is actually a group of genetically determined diseases in which there is a progressive degeneration of skeletal muscle (the muscles that are attached to the skeleton). Nerves and muscles work hand in hand, so damaged nerves will lead to damaged muscles.
Hereditary Myopathy of Labrador Retrievers
This disease is inherited as an autosomal recessive trait. Signs of weakness begin between 6 weeks and 7 months of age. There is a marked decrease in exercise tolerance. An affected pup may have difficulty holding up their head, bunny hop while running, and collapse after brief exertio. The disease may affect the muscles involved in chewing and swallowing, resulting in drooling and the development of megaesophagus. Exposure to cold greatly exacerbates the symptoms.
Sex-Linked Muscular Dystrophy
This disease affects Golden Retrievers, Irish Terriers, Samoyeds, Rottweilers, Belgian Tervurens, and Miniature Schnauzers. It is transmitted on the X chromosome from the dam. Affected pups are weak at birth and often die. Those who survive develop a stiff gait, drooling, muscle wasting, and stunted growth. The condition may stabilize temporarily by 6 months of age, but later progresses.
Bouvier des Flandres Myopathy
This disease affects only the muscles of swallowing, resulting in regurgitation and megaesophagus. Signs appear at about 2 years of age. With severe megaesophagus, the outlook is guarded.
Distal Myopathy of Rottweilers
This disease affects the legs and feet, producing an abnormal stance with splayed toes and weak hocks.
This disease affects Chow Chows, Staffordshire Terriers, Rhodesian Ridgebacks, Cavalier King Charles, Great Danes, Golden Retrievers, and Irish Setters. Signs appear when the pups begin to walk. They include stiffness upon rising and walking. This is followed by a progressive stiffening of the gait as the dog exercises.
The diagnosis can be suspected by finding high serum CPK levels. Many of these problems will require a muscle biopsy for an accurate diagnosis. one of the best places to send samples is the Comparative Neuromuscular Laboratory of the University of California at San Diego.
Breeding dogs can be tested by the Alfort School of Veterinary Medicine in Maisons-Alfort, France, to see if they carry the defect.
Hereditary Myopathy of Labrador Retrievers: Diazepam (Valium) given twice a day benefits some puppies. It is important to prevent stress and chilling, and to warm a pup quickly if she is exposed to cold. The disease often stabilizes or improves by 6 - 12 months of age. Many dogs are able to live a normal life. If drooling and megaesophagus develop however, the outlook is guarded.
Sex-Linked Muscular Dystrophy: There is no effective treatment and the long-term prognosis is poor. If these dogs survive to middle-age, many will die of cardiomyopathy.
Hereditary nervous system diseases are not common. Most run in families. Affected individuals should not be bred.
Please contact your veterinarian for more information regarding this condition.
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