Muscular Dystrophy In Dogs

Muscular Dystrophy (MD) is a congenital, non-inflammatory, progressive, degenerative muscular disease caused by mutations in the dystrophin gene. Dystrophyin, a muscle-membrane protein is important in maintaining the muscle’s structural integrity during contraction.

The mutation in the gene (X-linked recessive) disrupts dystrophin production, and its absence in the muscle impairs muscle membrane (sarcolemma) leading to a degeneration. This initiates a chain of destructive processes leading to death of the muscle cells and they are replaced with bony or fatty tissue, which hampers muscle function that can ultimately lead to a loss of the ability to walk.

Absence of dystrophin from the muscle or present in a reduced altered form has clinical significance. Complete absence of dystrophin is usually associated with the severe Muscular dystrophy, whereas the reduced form may cause the milder Becker variant (BMD).

This muscle-wasting disease is primarily seen in newborn dogs (at one to three months of age) or those less than one year old. This disease has predilection for males, while female cases have been documented but are often misdiagnosed.

• Stiff gait (bunny hops)
• Stiffness in muscles/Weakening of muscles
• Plantigrade stance (Walking with the entire sole of the foot ,the toes and metatarsals are flat on the ground)
• Progressive generalized weakness
• Difficulty swallowing
• Widespread muscle atrophy/ Loss of muscle mass
• Muscle enlargement (include tongues, esophagus, diaphragm)
• Difficulty swallowing
• Tremors
• Limb deformity
• Excessive drooling
• Resistance to exercise

There are no ways to prevent or reverse muscular dystrophy now.

A number of experimental therapies have been studied, including stem cell injections and gene therapy (exon skipping), but these therapies have not been approved for clinical use.

Anabolic Steroids may decelerate the progression of the condition, but in most cases, the disease remains deadly.

However, there are different kinds of drug treatment and therapy available to improve a dog’s quality of life and holdup the progression of symptoms.

There are no home remedies as this is basically an inherited disease. The only way of prevention is by eliminating affected dogs from the gene pool. Theoretically, this is so easy considering the fact that how early these dogs become symptomatic and the dogs won’t reach reproductive maturity.

However, the difficulty is the costly nature of genetic screening for the carrier. Currently, all dogs having MD traits (and, if any offsprings) should be neutered and spayed to prevent hereditary transmission.

Genetic testing is available to check whether there is a mutation in the dystrophin gene. This is used to find out whether a dog is affected with muscular dystrophy or clear of the mutation or an asymptomatic carrier of muscular dystrophy. Female dogs can be asymptomatic MD carriers.

Golden Retrievers genetic testing is performed to look for the specific mutation that has happened in this breed or not.

When dogs are diagnosed with muscular dystrophy, it is important to take measures to avoid breeding that dogs (if they do survive to adulthood) to remove muscular dystrophied dogs from the gene pool.

Golden Retriever, Irish Terrier, Belgian Shepherd, Brittany Spaniel, German Shorthaired Pointer, Labrador Retriever, Miniature Schnauzer, Pembroke Welsh Corgi, Rottweiler, Rat Terrier, Samoyed

Causes:

Muscular dystrophy in dogs is caused by a hereditary dystrophin gene mutation that interrupts the dystrophin protein production, resulting in progressive degeneration of skeletal and cardiac muscle. This Autosomal recessive inheritance of dystrophin-associated Muscular dystrophy explains why most of the reported cases have been male. One-third of MD cases occur due to new mutations in dystrophin gene.

Types:

There are a few types of muscular dystrophy that have been seen to affect dogs.

Golden Retriever Muscular Dystrophy (GRMD):

• This is similar to human Duchenne Muscular Dystrophy (DMD).
• An X-linked disease characterized by mutations in the DMD gene and the absence of protein dystrophin
• Golden Retrievers and Irish Terriers
• In addition to previously noted symptoms, affected dogs are also reported with heart muscle disease
• GRMD serves as a model for DMD in humans in trials and clinical studies

Canine X-linked Muscular Dystrophy (CXMD):

• Progressive, degenerative canine myopathy
• This is also pathologically similar to human DMD
• Serum creatine kinase (CK) levels are markedly elevated which indicates exercise-induced muscle injury may play a role in the dystrophic process
• Weakness, stunting, and gait abnormalities ( in 6- 9 weeks)
• Fibrosis, contractures, and muscle atrophy (in 6 months)

Centronuclear Myopathy of Labrador Retrievers(CNM):

Labrador Retrievers in North America, Europe, and Australia; in this type

Generalized loss of muscle tone and control has been noted in affected dogs as young as 6 months old

• Alleles: CNM= Centronuclear myopathy and N= Normal
• N/Ngenotype dogs: cannot transmit CNM variant to their litter.
• N/CNMgenotype dogs: They are not affected by CNM but only are carriers. 50% of CNM variant is transmitted to their offspring.
• CNM/CNMgenotype dogs: the puppies will have centronuclear myopathy (at least 25%).

Dysphagia-associated Muscular Dystrophy:

• This type affects Bouvier des Flandres in Europe
• Muscular degeneration of the esophageal and/or pharyngeal muscles
• This type affects their ability to swallow

Other variations of this disease may be seen for each affected breed, including Belgian Sheepdog, Brittany Spaniel, Groenendaeler Shepherd, German Shorthaired Pointer, Miniature Schnauzer, Pembroke Welsh Corgi, Rottweiler, Rat Terrier, and Samoyed.

Morbidity:

There are different types of muscular dystrophy and they can vary in terms of breeds they affect, what their symptoms are and which muscles they affect. Nonetheless, whatever the form of MD is, it always progresses and becomes increasingly worse— this means, that the longer the dog has the condition, the muscles get progressively weaker.

Consequently, most dogs with MD eventually lose the ability to walk. Still, some dogs with mild conditions may progress more slowly, while most of the forms quickly become severe and immobilize the dogs.

Diagnosis:

• Muscle biopsy
• Immunohistochemical staining test
• EMG
• EKGs and a neurological examination
• Serum creatine kinase test

Mortality:

Dogs affected with MD similar to DMD experience the same symptoms as humans. The dogs typically succumb to the disease by around age 2. Muscular dystrophy is a potentially life-threatening disease.

Prognosis:

The prognosis for muscular dystrophy is guarded. As the existing condition is life-threatening, rigorous treatment is usually necessary but there is no approved treatment protocol as of now. A healthy routine and home care are the best defenses available.

Contact your vet right away, if you notice any of the following:

• Stiff gait (bunny hops)
• Stiffness in muscles/Weakening of muscles
• Difficulty in swallowing

For MD dogs:

Low fat, low carbohydrate, and high protein meals

• Include protein from lean meats (lean beef), poultry, seafood, eggs, peas, broccoli, spinach, and kale.
• Fat-free or low-fat dairy products like cheese, yogurt, milk, etc

Supplements needed:

• Omega-3 fatty acids.
• Coenzyme Q10.
• Creatine
• Vitamin D and calcium

Sadly, the immediate future is bleak for MD dogs as the treatment cost of muscular dystrophy is concerned with the diagnosis alone since no treatment is available yet. Blood tests, Muscle biopsies, and specialist consultations may beyond your means.

Moreover, many treatment options for muscular dystrophy are still in the entire experimental phase and have not been reached outdoors by a research institution.