Dermatomyositis is a disease that inflames both the skin and the muscles, and it is seen almost only in Collies and Shetland Sheepdogs. Researchers describe it as an immune-mediated disorder of the small blood vessels, and the dog form is studied as a model for the childhood version of the disease in people. [1]
This guide covers what published studies say about the signs, diagnosis, causes and outlook. For other causes of hair loss, see hair loss in dogs.
Which dogs get it
- A 2017 genetic study notes that the disease is diagnosed almost exclusively in Collies and Shetland Sheepdogs, two closely related breeds, which points to a strong inherited component. [1]
- A 2014 report describes the disease as hereditary in Collies and Shetland Sheepdogs and their cross-breeds. [2]
- A 2015 report of a family of Working Kelpies says a genetic predisposition is known in certain breeds, mainly Shetland Sheepdogs and Collies, but also the Beauceron. [3]
- Other breeds occasionally get a similar condition, called dermatomyositis-like disease. [2]
When it starts
Age at onset varies. Many dogs show signs between about 7 weeks and 6 months of age, while others do not develop the disease until well into adulthood. [1] Severity also varies within one family: in two test matings described in the 2017 study, every Collie puppy was affected, but to different degrees, and the cross-bred puppies that developed the disease had milder forms. [1]
Signs on the skin
- The first signs are usually scaling and crusts on the face, the ears and the tail tip, or over the bony points of the legs and feet. [1]
- Over time some dogs develop hair loss and wider lesions that can leave scarring, with reddened skin and patchy color. [1]
- Lesions can last for weeks or months, and in some dogs they keep coming back. [1]
- Flare-ups are often linked to a trigger, and later stress such as sunlight (UV light) can make the disease worse. [1] A 2008 study says the severity of lesions varies and is thought to increase with stressful stimuli. [4]
Signs in the muscles
Muscle involvement shows up as wasting of the muscles of the head, trouble eating, drinking or swallowing, and an unusual high-stepping walk. [1] In the Working Kelpie family, signs included wasting of the chewing muscles, along with hair loss, crusts, skin ulcers, loss of color on the nose and lips, and abnormal claws, to varying degrees. [3]
How it is diagnosed
Your vet will look at the pattern of lesions, the breed and any relatives with similar signs. In the 2017 study, most affected dogs were confirmed by examining a skin biopsy under the microscope; the rest were diagnosed by a vet from the clinical signs after ruling out demodectic mange, a mite infection that can look similar. [1] Your vet may suggest further tests, including of the muscles.
What causes it
- The 2017 study describes the disease as immune-mediated and says it usually follows an environmental trigger, such as a vaccination or a viral infection. Anecdotal reports also mention stressful events before onset. [1]
- A 2008 study of Shetland Sheepdogs says earlier studies in the Collie suggest it is inherited in an autosomal dominant fashion with incomplete penetrance, meaning not every dog that carries the trait shows the disease. Its own work suggests the disease may be immune mediated, but it did not detect disease-specific autoantibodies. [4]
- The 2017 genetic study found that risk involves several genes at once: an immune gene type (MHC haplotype) plus variants in two other genes, PAN2 and MAP3K7CL. Nine of 27 gene combinations gave a high or moderate probability of disease and explained 93% of the cases studied. Dogs with more risk variants in those two genes tended to show the disease earlier. The authors note that the immune gene type is also common among healthy dogs. [1]
Treatment and outlook
There is no cure. Lesions can last for weeks or months and may return, and avoiding known triggers such as strong sunlight may help limit flare-ups. [1] How a dog does depends on how severe the skin and muscle disease is, so ask your vet what to expect for your dog. Your vet will choose any treatment; this guide does not name medicines or doses.
Look-alike conditions
- Other ischemic dermatopathies. Dermatomyositis belongs to a group of blood-vessel diseases of the skin, the ischemic dermatopathies, that share clinical and microscopic features but have different causes. Their lesions may affect the toes, tail tip, ear margins and bony points. Ischemic reactions to rabies vaccines may mimic familial dermatomyositis and can occur in any breed. [5] A 2025 paper lists the classic forms as familial dermatomyositis, a juvenile dermatomyositis-like disease in other breeds, reactions at a rabies vaccine site, a generalized vaccine-associated form and a generalized form with no known cause. [8] A 2019 study of 177 dogs with ischemic dermatopathy (not counting familial dermatomyositis) found toy and miniature Poodles, Chihuahuas, Maltese, Yorkshire Terriers and Jack Russell Terriers over-represented, and judged over half of the cases unlikely to be linked to vaccination. [6]
- Ulcerative dermatosis of Shetland Sheepdogs and Rough Collies. This syndrome had been suggested as a variant of dermatomyositis. A 2001 study of 8 dogs found it started in adult dogs in the summer months, with ring-shaped and winding ulcers on sparsely haired areas, and concluded it is a distinct disease. [7]
- Demodectic mange. This mite infection is one of the conditions vets rule out before diagnosing dermatomyositis. [1]
When to see your vet
- Crusts, scaling, sores or hair loss on the face, ears, tail tip or legs of a Collie, Shetland Sheepdog or a cross of these breeds. [1][2]
- Wasting of the muscles of the head, or trouble eating, drinking or swallowing. [1][3]
- A littermate or relative with these signs, since the disease runs in families. [1]
- Skin lesions that appeared after a rabies vaccination, in any breed. [5]
FAQ
Is dermatomyositis in dogs genetic?
Yes, in part. Earlier work in Collies pointed to dominant inheritance with incomplete penetrance, [4] and a 2017 study found that risk involves an immune gene type plus variants in two other genes, with an environmental trigger usually needed as well. [1]
At what age does dermatomyositis start?
Often between about 7 weeks and 6 months of age, although some dogs are not affected until adulthood. [1]
Can dermatomyositis be cured?
No. Lesions can last weeks or months and may come back, so the aim is to manage the disease with your vet. [1]
Can other breeds get it?
Other breeds occasionally get a similar dermatomyositis-like disease, [2] and reactions to rabies vaccines can mimic it in any breed. [5]
The bottom line
Dermatomyositis is an inherited, immune-mediated condition affecting skin and muscle, seen mainly in Collies and Shetland Sheepdogs, often starting in puppyhood, with crusts, scaling and hair loss on the face, ears, tail tip and legs and, in some dogs, wasting of the head muscles. [1] Sunlight and other stresses can make it worse, and lesions may keep coming back. [1] If you see these signs, especially in a young dog of these breeds, see your vet.
This article is for general information and is not a substitute for a veterinary exam. If you are worried about your dog’s skin, see your veterinarian.
Sources
- Evans JM, Noorai RE, Tsai KL, Starr-Moss AN, Hill CM, Anderson KJ, Famula TR, Clark LA. Beyond the MHC: A canine model of dermatomyositis shows a complex pattern of genetic risk involving novel loci. PLoS Genet. 2017;13(2):e1006604. doi:10.1371/journal.pgen.1006604. Open access (CC BY), PubMed Central PMC5315411. https://pmc.ncbi.nlm.nih.gov/articles/PMC5315411/
- Bresciani F, et al. Dermatomyositis-like disease in a Rottweiler. Vet Dermatol. 2014;25(3):229-e62. doi:10.1111/vde.12128. PMID 24797324. https://pubmed.ncbi.nlm.nih.gov/24797324/
- Röthig A, Rüfenacht S, Welle MM, Thom N. Dermatomyositis in a family of Working Kelpies. Tierarztl Prax Ausg K Kleintiere Heimtiere. 2015;43(5):331-336. doi:10.15654/TPK-141112. PMID 26105578. https://pubmed.ncbi.nlm.nih.gov/26105578/
- Wahl JM, et al. Analysis of gene transcript profiling and immunobiology in Shetland sheepdogs with dermatomyositis. Vet Dermatol. 2008;19(2):52-58. doi:10.1111/j.1365-3164.2008.00655.x. PMID 18336421. https://pubmed.ncbi.nlm.nih.gov/18336421/
- Morris DO. Ischemic dermatopathies. Vet Clin North Am Small Anim Pract. 2013;43(1):99-111. doi:10.1016/j.cvsm.2012.09.008. PMID 23182327. https://pubmed.ncbi.nlm.nih.gov/23182327/
- Backel KA, Bradley CW, Cain CL, Morris DO, Goldschmidt KH, Mauldin EA. Canine ischaemic dermatopathy: a retrospective study of 177 cases (2005-2016). Vet Dermatol. 2019;30(5):403-e122. doi:10.1111/vde.12772. PMID 31297888. https://pubmed.ncbi.nlm.nih.gov/31297888/
- Jackson HA, Olivry T. Ulcerative dermatosis of the Shetland sheepdog and rough collie dog may represent a novel vesicular variant of cutaneous lupus erythematosus. Vet Dermatol. 2001;12(1):19-27. doi:10.1046/j.1365-3164.2001.00212.x. PMID 11301535. https://pubmed.ncbi.nlm.nih.gov/11301535/
- García N, Cobos À, Solano-Gallego L, García M, Ordeix L. Clinical, Immunological and Pathological Characteristics of Ischemic Dermatopathy in Dogs with Leishmaniosis. Pathogens. 2025;14(3):246. doi:10.3390/pathogens14030246. Open access (CC BY), PubMed Central PMC11944567. https://pmc.ncbi.nlm.nih.gov/articles/PMC11944567/