Myopathy In Dogs: Causes & Types

Myopathy is simply defined as a disease derived from the skeletal muscle and the disease should be unrelated to any disorder of innervation or neuromuscular junction or does not arise secondarily from disorders of the nervous system. The primary symptom of myopathies is muscle weakness due to dysfunction of muscle fiber.

“Myopathy” in Greek literally means “myo” (muscle) and “pathos” (disease).

These are groups of disorders that are characterized by a primary structural or functional impairment of the skeletal muscle.

The most consistent and most common clinical indicator of myopathy is ‘Weakness’. The affected dogs will be unable to carry out tasks that involve the use of proximal muscles, such as getting up from a lying position, climbing steps, or lifting toys. Distal problems are uncommon, but not forget that they can be the determining symptom in certain types of myopathies such as genetic distal myopathies, hereditary inclusion body myositis, and myotonic dystrophy.

There are different types of myopathies that can be broadly classified into Inherited myopathies and acquired myopathies. As their name suggests, inherited myopathies are inherited whereas acquired myopathy may happen due to several reasons such as autoimmune disorder, a metabolic or endocrine disorder.

Congenital myopathy symptoms:

• Muscle weakness
• Exercise intolerance
• Respiratory impairment
• Bulbar muscle dysfunction
• Wasting(atrophy)
• Drooping eyelids
• Facial weakness
• Paralysis
• Rigidity/stiffness/swelling
• Fatigue

Acquired myopathy symptoms

• Myalgias(Muscle soreness) with occasional contractures
• Cramps
• Myotonia
• Myoglobinuria
• Muscle wasting around the shoulders and hips
• Sudden weakness on one side of the body
• Impaired sounds
• Cause difficulty swallowing (dysphagia)
• Regurgitating (Megaesophagus)
• Weakness of the eye muscles (ocular myasthenia)
• Drooping of one or both eyelids (ptosis)

There is no specific cure for myopathies but they can be treated to relieve symptoms. Depending on the underlying cause, vets may recommend one or a combination of these treatments:

Treatment of diseases of infectious origin: Antibiotics, antivirals, antiparasitics, etc

Treatment of diseases of tumor origin: Surgery, chemotherapy

Treatment of inflammatory or immune-mediated diseases: Immunosuppressive drugs

1. Immunosuppressive therapy:

The acute phase should be treated properly, or else it can progress to the chronic phase

Prednisone at 2 - 4 mg/kg PO (4 to 6 months, with no more than a 50% decrease in the dose every month)

After which a minimal maintenance dose to subside clinical signs is enough.

• Azathioprine: 2 mg/kg PO q24 then 48h
• Methotrexate: 2.5 mg/mL
• Leflunomide: 2 mg/kg/d
• Mycophenolate: 10mg/kg PO q12h
• Cyclosporine (immunomodulator): 5mg/kg PO q12h

2. Once the disease is being controlled, shift towards the long-term goal. The medications are slowly reduced and eventually get your dog completely off all medications. However, most cases require continual use of a minimal dose of medication.

3. Physical therapy: Some dogs may require physical therapy depending on the severity of the disease. Physical therapy is done to enhance muscle strength.

1. Appetize the dog food: stimulate dog's appetite with attractive foods for dogs that lost their appetite

Adding chunks of meat such as lamb or chicken helps to stimulate their appetite. Add some warm broth to their food (homemade broth is ideal) and also stimulates the appetite.

2. A dog with muscle weakness will need more specialized foods than normal to help bolster its activity. For example, dogs with injuries will need extra protein, dogs with aging-related problems will need more fiber and dehydrated dogs will need wet food.

3. Make sure to provide an environment conducive to your dog’s recovery

Obviously, optimizing your pet’s muscles should be the top priority for preventing muscle conditions from happening in the first place.

Diet: Nutritionally balanced, wholesome diet formulated for the dog’s size and lifestyle

Weight: Maintenance of ideal weight for the dog

Exercise: Right amount of exercise, low-intensity exercise such as hydrotherapy

Supplements: Joint, bone, and spine supplements

German Shepherd, Belgian Shepherd, Doberman Pinscher, Saint Bernard, Old English Sheepdog, Akita, German Shorthaired Pointer, Golden Retriever, Terrier Dog Breed, Boxer, Great Dane, Cocker Spaniel, Springer Spaniel, Smooth Fox Terrier, Jack Russell Terrier

Causes:

1. Hereditary: Some dogs may be predisposed genetically to myopathy.
2. Suspected triggers of myopathy include:

• Bacterial and/or viral infection
• Trauma
• Exposure to allergens/ environmental toxins
• Idiopathic: the actual trigger of MMM is not known

Types:

1. Hereditary Myopathy:

Muscular Dystrophies: Progressive, a degenerative muscular disease caused by mutations in the dystrophin gene

Metabolic Myopathy: Muscular disorders caused by the inability to properly convert food into energy due to a lack of enzymes required for metabolism

Mitochondrial Myopathy: Group of neuromuscular diseases caused by damage to the energy-producing structures in the cells called mitochondria

Channelopathies: Heterogeneous group of disorders due to dysfunction of ion channels or their interacting proteins.

2. Acquired Myopathy:

Inflammatory Myopathy: Group of disorders characterized by inflammation of the skeletal muscles with no known cause.

Endocrine Myopathy: Myopathy is caused by too much or too little hormone production from the endocrine glands (e.g. thyroid gland).

Toxic Myopathy: Myopathy is caused by certain drugs and toxins.

Infectious Myopathy: An infection causes myopathy and prevents the muscles from functioning properly.

Morbidity:

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

Mortality:

Myopathy is not potentially life-threatening and there is no documented mortality rate.

Diagnosis:

• Nerve and muscle biopsy
• Biochemical and genetic testing
• CT scan and MRI
• Lumbar puncture (spinal tap)
• Nerve conduction studies and electromyography (EMG)

Prognosis:

With early detection, Most myopathies carry a favorable prognosis, although they are a difficult group of diseases to manage. Relapses occur rapidly so treatment should not be discontinued prematurely.

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

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, milk, yogurt, etc

Supplements needed:

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

Foods to avoid:

1. Salt-heavy diet
2. Avoid dairy products
3. No to fried, ultra-processed, Hard, or jagged foods (such as Crunchy crackers, chips, etc)
4. Hard to digest grains and greasy foods
5. No treats or tossing the leftovers

Myopathy restricts your dog from living its life to the fullest. Identification of myopathy in dogs can be challenging, sometimes even for veterinarians.

However, early detection and a tailored treatment plan do a world of good for myopathic dogs, and, in many cases; this prevents the progression of any underlying condition to an irreversible or a more serious state.