Canine dermatomyositis (DMS)
Canine dermatomyositis (DMS) is an inherited autoimmune disease of the skin and muscle. Although it is influenced by genetic heritage, environmental components also contribute to the development of the disorder. In human patients, disorder clinically, histologically and immunologically similar to DMS is known as juvenile dermatomyositis (JDM). DMS has been diagnosed so far only in Collie and Shetland sheepdog breeds, which are genetically and phenotypically similar, which suggests the origin of the causative gene in an ancestor common to both breeds. Signs similar to DMS has been reported in other breeds; Welsh Corgi, Lakeland Terrier, Chow Chow, German Shepherd, and Kuvasz.
Characteristics and symptoms
First canine dermatomyositis symptoms appear in young dogs, usually by 6 months of age, but may appear as early as 7 to 11 weeks of age. and earliest clinical signs include crusting and scaling on the face, ears, tail tip, and across the bony prominences of the limbs and feet. The skin lesions may get worse with disease progression and alopecia may occur as well. Lesions usually heal within weeks or months, but may also chronically reoccur. Head musculature shows signs of atrophy, which can be noticed by difficulty eating, drinking and swallowing, as well as atypical, high-stepping gait. DMS usually develops as a response to an environmental trigger, which can be viral infection or stressors such as UV light. Diagnosis until now was possible by biopsy of affected skin and muscle.
Canine dermatomyositis is caused by a mutation within three different loci, genes PAN2, MAP3K7CL, DLA-DRB1. DNA testing analyses presence of genes connected to the higher risk of disease development, allowing the risk assessment. Pedigree analysis reveals a complex mode of inheritance, influenced also by environmental factors.
Evans JM, Noorai RE, Tsai KL, Starr-Moss AN, Hill CM, Anderson KJ, et al. (2017) Beyond the MHC: A canine model of dermatomyositis shows a complex pattern of genetic risk involving novel loci. PLoS Genet 13(2): e1006604. https://doi.org/10.1371/journal.pgen.1006604