Dermatomyositis describes an inflammatory condition affecting the dermis, connective tissues and to a variable degree, muscular tissues of young dogs. Dermal lesions typically comprise erythema, dermatitis and/or alopecia of the extremities, digits, ears and face. Affected animals are typically less than 1 year of age. Many develop subsequent myositis (notably affecting the muscles of mastication and/or locomotion). Commonly affected breeds include the Shetland Sheepdog and the Collie breeds.