Dermatomyositis in Dogs

Category: Skin & Connective Tissue
Inheritance: Multifactorial
Breeds documented: 1
Published sources: 3

Overview

Inflammation in the skin and muscles is the main problem in dermatomyositis. Early damage involves small blood vessels and can lead to loss of skin and muscle tissue. Typical skin changes include crusts, sores and lost hair, particularly around the face, ears, legs and tail tip. Severity varies: some dogs have mainly skin changes, while others develop muscle weakness that affects eating, swallowing or walking.

Signs to watch for

Patchy hair loss and crusts on the face or ear tips
Sores on the tail tip, legs or feet
Loss of muscle bulk around the head
Difficulty eating, drinking or swallowing
An unusual way of walking

Signs usually appear in puppyhood, although adult onset is possible.

When to get help Contact your vet promptly if skin sores appear with difficulty eating or swallowing.

Diagnosis and tests

Vets consider the skin changes, muscle signs and family history, including affected littermates. Small samples of skin and muscle, called biopsies, and electrical testing of muscles can help establish the diagnosis. A DNA risk test is available for Collies and Shetland Sheepdogs; it estimates susceptibility rather than confirming that a dog is ill.

Breeds with documented risk

1 breed

By breed size

1 Medium

CollieMedium · Herding Group

Inheritance

This condition has more than one known form, and different breeds inherit it in different ways. The sources list the form found in each breed.

Multifactorial
Collie, Shetland Sheepdog
Several genes and the environment together set the risk. Diet, growth rate, weight and exercise can all play a part. There is no single DNA test. Screening the parents (for example hip or elbow scores) and choosing from lines with good results lowers the risk, but does not remove it.
As stated by UC Davis VGL
Autosomal dominant
Collie
One copy of the variant, from either parent, is enough to put a dog at risk. On average, an affected dog passes the variant to half of its puppies. Males and females are affected equally.
As stated by Merck Veterinary Manual

We've gathered what published sources say about this condition, so you can talk it through with your vet. It isn't veterinary advice: you and your vet know your dog best.