Golden Retriever Muscular Dystrophy (GRMD)

Golden Retriever muscular dystrophy or GRMD, is a progressive, degenerative disorder that negatively impacts a dog's muscles and their ability to move. The disorder is a genetically inherited condition that typically affects male dogs more than their female counterparts because the defect responsible is the chromosome x. However, female dogs too can inherit the disorder should they inherit two defective alleles. Any dogs known to suffer from Golden Retriever muscular dystrophy should be spayed or neutered so they cannot be used for breeding purposes.

Breed Most Affected

As the name of the disorder suggests, this inherited condition affects Golden Retrievers. However, the good news is that it is rarely seen in the breed.

The Causes

As previously mentioned, GRMD is a rare genetic disorder that negatively impacts a dog's muscles. The disease affects a vital protein known as dystrophin. It is thought the condition is caused by a reduced production of a much-needed growth hormone. As a result, it means a dog's muscles are negatively impacted and in some cases, they are affected to such an extent that dogs can hardly move. Research also suggests that the defective gene is probably passed from male to male.

Symptoms Associated with the Disorder

Dogs that inherit the condition start to show signs of there being something seriously wrong with them when they are around eight weeks old. The symptoms most commonly associated with GMRD include the following:

• Muscle weakness
• Difficulty walking
• Difficulty breathing
• Drooling excessively
• Intolerance to exercise

Should the symptoms be very severe, puppies don't normally survive more than a few days, but those with milder symptoms can often live for several years. When dogs start to show signs of there being something wrong when they are a little older at around three to four months old, symptoms often include the following:

• Poor weight gain
• Cow hocks
• Hypoglycemia
• General weakness
• Abnormal heart rate
• Muscle atrophy – lack of muscle tone

The disorder is typically classed in three stages being Grade I, Grade II and Grade III with the latter being the more severe with dogs succumbing to the symptoms when they are anything from six to twelve months of age.

Diagnosing the Condition

A vet would need to know a dog's ancestry and how any symptoms first presented themselves to make a preliminary diagnosis. The sort of tests the vet would recommend carrying out to confirm a diagnosis would be as follows:

• A muscle biopsy
• Immunohistochemical analysis which would establish if levels of dystrophin protein have been negatively impacted

Blood tests often don't reveal enough information other than if a dog's creatinine kinase levels are higher than they should be. With this said, a vet would want to rule out any other health issues which could be causing the problem and this includes the following disorders:

• Polymyositis
• Nemaline myopathy
• Duchenne muscular dystrophy
• Toxoplasma gondii
• Hepatozoon americanum
• Sarcocystis neurona
• Neospora spp
• Hammondia hammondi
• Masticatory muscle myositis
• Tetanus
• Myasthenia gravis
• Thymoma
• Dermatomyositis

Treatment Options

Sadly, there are no treatment options for dogs suffering from the condition. However, a lot of research is being carried out and one treatment which involves gene replacement is showing promising results. The end goal of treating a dog suffering from the disorder would be to offer supportive care more especially in very young puppies that are still suckling and are having problems doing so. Some puppies do show signs of improvement and often gain weight to some extent, although the prognosis always remains guarded when it comes to their survival rate.

Testing for Golden Retriever Muscular Dystrophy

There is a genetic test for Golden Retriever muscular dystrophy which can be carried out of dogs at any age. The test has proved to be very accurate and establishes whether a dog is affected by the condition, whether they are carriers or clear of the gene responsible for the disorder. Results of the tests are as follows:

Affected - this establishes whether a male dog carries the gene mutation and whether females carry both alleles

Carrier - this establishes whether a female is a carry of one gene mutation

Clear - this establishes that dogs do not carry the gene mutation and that they are therefore, healthy and can be used for breeding purposes