Dermatomyositis is an inherited condition characterized by the inflammation (itis) of the skin (dermato) and muscles (myo) that is typically seen in young collies, sheetland sheepdogs and their crossbreeds. The condition can occasionally affect the blood vessels as well.
Dermatomyositis is inherited from both parents (autosomal dominant manner). The lesions of the skin develop before six months of age, sometimes as early as seven weeks. By the time the affected puppy reaches one year of age, the full extent of lesion is present. Development of this condition in later ages does happen but it is rare.
In this condition, the skin lesions typically develop first with variable muscle problems occurring later. The lesions commonly occur on dog's face, around the eyes and tips of the ears. They may also occur at the tip of the tail, the toes and other bony prominences. The lesions are similar to blisters or small bumps, with skin reddning and loss of hair at the affected sites. Blisters then turn into crusts. in due time, the affected skin scars and the hair loss becomes permanent.
Muscles are not always severely affected in dermatomyositis. When they are, the puppy will be weak and lethargic. The growth rate will be slow with smaller than normal muscles, specially of face and head.The esophagus may be enlarged (mega esophagus). Where muscles are severely affected, the dog may have difficulty chewing or swallowing.
Common symptoms of this condition include skin lesions, blisters, skin crusting, muscle atrophy, hair loss at the affected sites, difficulty chewing or swallowing, slow growth rate, weakness, lethargy and pneumonia.
