Dermatomyositis is an autoimmune disease that attacks the skin and muscular tissue. Dogs with dermatomyositis first develop skin lesions and progresses to include generalized muscle atrophy. Initial lesions are typically found on the face and may also appear on the feet, legs, and tail. Lesions come and go and vary in severity. If muscle atrophy is severe it can interfere with eating, drinking, lameness, and infertility. Dermatomyositis can cause secondary megaesophagus, a condition in which the esophagus balloons and interferes with swallowing and the passage of food to the stomach. Dermatomyositis usually begins before six months of age but can occur during adulthood.
Diagnosis can be difficult and may require biopsy or electromyography, a test of muscle function. It is treated with drugs that improve circulation and reduce inflammation. Antibiotics may be necessary for secondary infections of skin lesions.
Dermatomyositis is a type of autoimmune disease. Autoimmune diseases are genetically predisposed; if a dog has the disease, it has the genes. Dogs affected with Dermatomyositis should not be bred. Their near relatives should not be bred to mates with a family history of any autoimmune disease.