Non-Inflammatory, Hereditary Muscle Disease in Dogs

Dystrophy-like muscular diseases may begin to show their presence in the first weeks to first months of a dog’s life. Muscle atrophy is a distinct sign of the affliction, leading to further complications. Progression will vary from dog to dog, and studies to date have stated that this condition tends to affect male dogs predominantly.

Non-inflammatory muscle disease (myopathy) is classified as a progressive condition, resembling muscular dystrophy in humans. Ongoing muscular degeneration is the outcome, and this inherited condition is primarily documented in young dogs.

The symptoms of two types of inherited muscle disease are listed below. If your furry family member is exhibiting any of these concerning behaviors, contact your veterinarian for testing and advice.

• Dystrophin deficient myopathy
Bilateral muscle weakness

Difficulty swallowing (dysphagia)
Regurgitation
Stiff gait
Loss of muscle mass
Plantigrade stance (walking with full footpads on the ground)
Pain
Limited joint mobility
Hunched posture
Accompanying heart muscle disease (signs may be breathing abnormalities)

• Labrador Retriever Myopathy
• Severe muscle weakness
• Exercise intolerance
• Stiff or abnormal gait
• Arched back
• Stunted growth
• Abnormal joint posture
• Forward bending of the head and neck
• Jaw spasms in which the mouth closes tightly (trismus)
• Swelling and enlargement of muscle
• Enlarged esophagus (megaesophagus) resulting in vomiting or regurgitation

Types

There are several types of hereditary muscle disease known to affect canines.

• Dystrophin deficient myopathy
• This muscle disease is known as X-linked muscular dystrophy
• It is caused by a gene on the X chromosome
• It results because of a deficiency or alteration of dystrophin (crucial in stabilization of muscle fiber membranes during contraction)
• Typically males are affected
• Breeds predisposed are Terriers, Golden and Labrador Retrievers, Rottweilers, German Shorthaired Pointers, Belgian Shepherds, Brittany Spaniels, Japanese Spitz, Samoyeds, and Miniature Schnauzers
• Labrador Retriever Myopathy
• This condition is possibly autosomal recessive
• Both black and yellow canines of this breed are affected
• Cold and exercise exacerbate the condition
• Males and females are represented
• The disease has been recently renamed centronuclear myopathy

Some of the other hereditary muscle diseases found in dogs are congenital myotonia (Chow Chows and Staffordshire Terriers are prone), and sarcoglycan deficiency (Cocker Spaniels, Chihuahuas, and Boston Terriers are predisposed).

Inherited muscle diseases are due to genetic and hereditary factors, as these examples show.

• Dystrophin deficient myopathy is caused by a mutation in the dystrophin gene, leading to a degeneration of muscle fibers
• Labrador Retriever myopathy results from a type 2 muscle fiber defect
• Congenital myotonia is due to a defect in the chloride channels
• Sarcoglycan deficiency is caused by a reduced amount of proteins responsible for connecting the muscle fiber
• Non-breeding of dogs known to have hereditary muscle disease is the responsible choice

The diagnosis of muscular dystrophy in your pet will be an extensive process. Your veterinarian will want to rule out a differential diagnosis that could cause some of the same symptoms. For example, peripheral nerve neoplasia (abnormal cell growth), arthritis, metabolic or systemic disease, and respiratory insufficiency could all have symptoms that mimic muscle degeneration.

The visit with the veterinarian will commence with a few questions.

• What are the symptoms you have seen that are causing concern?
• What are the typical exercise patterns of your dog?
• How long have his muscles seemed weak or stiff?
• Does he have a good appetite?
• Have you seen any usual behaviors like regurgitation or difficulty swallowing?

After a physical and neurological examination, your veterinarian will look for further diagnostic information in the form of a complete blood count, biochemistry, and urinalysis. The serum creatine kinase and enzyme levels seen can be particularly telling when searching for answers to muscular dystrophy.

A muscle biopsy could be suggested, which will reveal variations in muscle size, and degree of atrophy. A electromyography can assess the general health of the muscle. DNA tests can prove certain mutations known to be evident in hereditary muscle disease.

Unfortunately, there are no known cures or treatments for non-inflammatory hereditary muscle disease. Minimal drug therapy is available; for instance, the use of glucocorticosteroids is sometimes attempted in the case of dystrophin deficient myopathy, but in reality, the disease is progressive.

Eventually, many dogs will face debilitation, and some will have heart muscle disease. However, it should be noted that the progression will vary in each dog diagnosed with muscular atrophy. Some will face a rapid degeneration of muscle, while others will remain healthy and relatively active for some time.

Physiotherapy and supportive measures on your part (like providing soft bedding and regular, gentle exercise), can help pets who have this condition. There is a positive outlook for our canine friends who have been diagnosed with Labrador Retriever myopathy; this condition can stabilize once the dog reaches maturity.