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Myotubular Myopathy

Myotubular Myopathy is a disorder that affects the muscle cells. This starts with an early-onset hind limb weakness, progressing to an inability to move.

Key Signs

Progressive muscle weakness, Muscle atrophy, Absence of patellar reflexes, Inability to rise and walk

Age of Onset

0 to 2 yrs

Juvenile onset

Inheritance

X-linked Recessive

For X-linked recessive disorders, the genetic variant is found on the X chromosome. Female dogs must have two copies of the variant to be at risk of developing the condition, whereas male dogs only need one copy to be at risk. Males and females with any copies of the variant may pass the disorder-associated variant to their puppies if bred.

Likelihood of the Condition

High likelihood

At risk dogs are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with Myotubular Myopathy

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about Myotubular Myopathy

The clinical signs of X-linked myotubular myopathy can be seen in puppies as young as 10-19 weeks of age. Pelvic limb weakness is typically observed as one of the first signs. Affected dogs also lack patellar reflexes. XLMTM is characterized by rapidly progressing muscle weakness and muscle atrophy. Affected dog won't be able to rise and move unassisted within a few weeks of the onset of clinical signs and may also have difficulties chewing and swallowing. Excessive autophagy and prominent autophagic vacuoles are seen upon histopathology.

As the disorder is progressive, the welfare of affected dogs should be monitored closely. Owners of affected dogs should be advised that their dog will require assistance with movement and that clinical signs are likely to progress rapidly.

For Breeders

Planning to breed a dog with this genetic variant?

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disorder is X-linked recessive, meaning the genetic variant is found on the X chromosome. Given males only have one X chromosome, a single affected copy will increase the risk of being diagnosed with the disorder. Females typically require two copies to be at an elevated risk. Use of dogs with one or two copies of the variant is not recommended for breeding as there is a risk that the resulting litter will contain affected puppies. Please note: It is possible that clinical signs similar to the ones caused by this variant could develop due to a different genetic or clinical cause.

Technical Details

Gene MTM1
Variant A>C
Chromosome X
Coordinate 118,901,282

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Shelton, G. D., Rider, B. E., Child, G., Tzannes, S., Guo, L. T., Moghadaszadeh, B., … Beggs, A. H. (2015). X-linked myotubular myopathy in Rottweiler dogs is caused by a missense mutation in Exon 11 of the MTM1 gene. Skeletal Muscle, 5(1). View the article