Hereditary myopathy - Labrador retriever/Bouviers des Flandres myopathy

What is ... ?: 

Hereditary myopathy means an inherited disease of muscle. Labrador retriever myopathy is a rare inherited disease which causes muscle weakness because of a deficiency of type II muscle fibres. The first sign is an abnormal, stiff gait, which progresses to a generalized weakness by about 5 months of age.
Bouvier des Flandres myopathy is another rare disease causing generalized muscle weakness. Megaesophagus is common.

How is ... inherited?: 

In Labrador retriever myopathy, the mode of inheritance is autosomal recessive. The mode of inheritance is unknown in the Bouvier.

What does ... mean to your dog & you?: 

Labrador retriever myopathy: The first thing you may notice is that your Lab puppy has an abnormal gait (sometimes called "bunny-hopping"). By around 5 months of age, your pup's growth will be stunted, and s/he will have generalized weakness which may come and go, and will probably be worse with exercise, excitement, or cold temperatures. As the condition worsens, the muscles will atrophy (shrink), making certain bones appear to protrude abnormally. Other than the muscle weakness, most dogs remain bright and alert, and in many, the disease will stabilize and clinical signs will not worsen beyond 6-8 months of age. Some dogs will show gradual improvement.
There is no specific treatment or cure for this disease. Dogs that are severely affected will become very debilitated. Others who are only mildly affected have a good prognosis for a quiet life.
Bouvier des Flandres myopathy: The disorder becomes evident in young adults (around 2 years of age), who have a peculiar gait, generalized weakness which becomes worse with exercise, and muscle atrophy (shrinkage).  Megaesophagus is common with this condition in the Bouvier, causing regurgitation after eating and the potential complication of aspiration pneumonia.

How is ... diagnosed?: 

Labrador retriever myopathy: This disease is one of the rule-outs your veterinarian will consider if your young Labrador retriever (6 weeks-7 months of age) shows signs of muscle weakness. To reach a diagnosis, your vet may   measure the response of muscles to electrical stimulation (electomyography) and will take muscle samples (muscle biopsies) from your dog  for evaluation by a veterinary pathologist.
Bouvier des Flandres myopathy: Diagnosis is confirmed by electromyography.

How is ... treated?: 

There is no cure for either disease. Some of the clinical signs of Labrador retriever myopathy may be reduced with medication such as diazepam. There is no specific treatment for megaesophagus, but it may be managed by feeding small, frequent, high-caloric meals from an elevated location so that gravity assists the passage of food. Different consistencies of foods can be tried to determine which causes the least regurgitation.

For the veterinarian: 

CK is elevated in both conditions. Profound creatinuria (up to 30 times normal) is common with Labrador retriever myopathy.

Breeding advice: 

Affected Labrador retrievers, and their parents (carriers of the trait) and siblings (suspect carriers) should not be bred. Although the inheritance in Bouviers is unknown, affected animals should not be bred, and it is preferable to avoid breeding their parents or siblings animals as well.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources: 

Kornegay JN. 1995. Disorders of the skeletal muscles. In EJ Ettinger and EC Feldman (eds) Textbook of Veterinary Internal Medicine, pp.727-736. WB Saunders Co., Toronto.

Ackerman L. 1999. The Genetic Connection: A Guide to Health Problems in Purebred Dogs, 115-116. AAHA Press,Lakewood, Colorado.


What breeds are affected by ... ?
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