Dermatomyositis in Dogs

Collie at animal hospital

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Dermatomyositis is not as common as some other diseases that dogs can get, but it is a serious condition that affects the skin and muscles of certain breeds of dogs. Recognition of this disease can aid in early management and therefore keep a dog with dermatomyositis comfortable for a longer period of time.

What Is Dermatomyositis?

Also diagnosed in people, dermatomyositis is considered a hereditary or genetic disease. It is not fully understood but veterinary professionals recognize it as an immune-mediated condition that affects the muscle and skin of dogs. It causes a variety of symptoms, but skin lesions are most commonly seen. Puppies who exhibit symptoms of dermatomyositis seem to be more severely affected than adult dogs that develop it.

Symptoms of Dermatomyositis in Dogs

Most commonly identified by crusted and inflamed lesions on the face or ears, symptoms of dermatomyositis will typically be either skin or muscle issues. Skin lesions can be painful, bleed, and stay on the face or spread all over the body, but the severity of the disease will vary from dog to dog. Owners often initially report seeing sores on the face of their puppies, but signs are often initially ignored or not even noticed. Some puppies will have a decrease in muscle mass, be weak and lethargic, and even have problems swallowing due to a condition known as mega-esophagus. Some dogs with mega-esophagus will need to be fed sitting upright or they will be unable to keep food in their bodies making this symptom difficult to manage. As muscle weakness persists in dogs, facial palsy, stiffness, and difficulty walking will develop.

Adult onset of dermatomyositis is rare so this is primarily a disease of puppies. Symptoms may appear as early as seven weeks of age but are typically seen by the time a puppy is six months of age.

Signs

  • Lesions resulting in hair loss
  • Crusty lesions
  • Ulcerated lesions
  • Lesions on the face, ears, around the eyes, tip of tail, or pressure points
  • Muscle atrophy
  • Weakness
  • Mega-esophagus


Causes of Dermatomyositis

The cause of dermatomyositis is unfortunately not fully understood but it is known that it is a hereditary condition that is passed on from dog to dog in their DNA. There is a definite familial tendency, which means that if a parent dog has dermatomyositis then it will likely be passed on to its offspring. Some research suspects vaccinations, exposure to UV light, and other environmental triggers may even play a role in this auto-immune disease development in dogs. Dermatomyositis has been studied in both humans and dogs for decades and seems to be very similar in the two different species.

Treatment

Symptomatic treatment is heavily relied on for dogs with dermatomyositis. There is no cure for this inherited disease, so the goal is to simply keep the dog as comfortable as possible for as long as possible. Medications and vitamins used to manage dermatomyositis can get expensive, and at-home care can become labor intensive.

Pentoxifylline, vitamin E, prednisone, azathioprine, and cyclosporine are common options to manage dermatomyositis. Avoiding UV light exposure and activities that can further damage the skin are also important. Other at-home care may include offering assistance with feeding to dogs who have difficulty swallowing and utilizing special shampoos at bath time.

How to Prevent Dermatomyositis

A genetic test is available to test a dog for the risk level of developing dermatomyositis, but this unfortunately cannot help a dog who is at high risk. Selective breeding is the best way to prevent dermatomyositis in predisposed breeds of dogs. Dogs who have been diagnosed with dermatomyositis, along with their first degree relatives, should not be bred in order to lessen the likelihood of passing on the genetics for developing dermatomyositis.

Vaccinations should be discussed with your veterinarian (but not necessarily avoided) to determine what your specific dog needs. Exposure to UV light and extreme environmental changes should also be monitored in case these may be triggers for dermatomyositis to develop in at risk dogs.

What Breeds Are Prone to Dermatomyositis?

In dogs, dermatomyositis seems to be mainly isolated to Collies and Shetland Sheepdogs, but some other breeds have reported similar symptoms. These other potential breeds that may develop dermatomyositis include Chow Chows, Pembroke Welsh Corgis, Lakeland Terriers, German Shepherds, Beaucerons, Kuvasz, and breeds mixed with them.

Diagnosis

A skin biopsy is the most commonly used method to diagnose dermatomyositis in dogs. To perform a biopsy, a sample of a skin lesion is taken and evaluated in a laboratory. This skin sample will be examined microscopically. To obtain this biopsy sedation or local anesthesia will most likely be utilized. Other skin diseases, including mange and ringworm, may also be ruled out by performing other tests prior to a skin biopsy. On a rare occasion, a muscle biopsy and a test called an electromyogram may also be performed to diagnose dermatomyositis.