Dog Health by LowchensAustralia.com

Dermatomyositis

Information on dermatomyositis is available to veterinarians and the lay public in a variety of veterinary publications. The newest and most widely available is in Muller and Kirk's: Small Animal Dermatology - 5th ed. Philadelphia: W.B. Saunders, 1995, pages 759-764. If the information below is published, please put that reference as the source so your readers and their veterinarians will know where to go to get more complete details. There is also some more information on this site, courtesy of Kim Schive.

1. Recognized in many different breeds but especially common in Collies and Shelties.
   
   
2. Both the skin and muscle can be involved. It is very unusual to have muscle signs without skin disease. In most cases, only dogs with moderate to severe skin lesions have clinically significant muscle disease. The skin disease may or may not be active when the muscle disease is recognized.
   
   
3. Although there appears to be a rare adult-onset variant, most affected dogs develop skin lesions early in life. Typically, skin lesions are first seen in dogs 12 to 24 weeks of age. The lesions may be short-lived or persist and worsen over the next several months.
   
   
4. Skin lesions occur in areas of trauma. The gums, tips of the pinnae [ears], skin on the bridge of the nose and face, skin over the joints and toes of the limbs, and tip of the tail are common sites of involvement.
   
   
5. Skin lesions can heal rapidly without treatment or persist and worsen with time. In dogs which don't heal rapidly, it can take months before the extent of the skin lesions is known.
   
   
6. Skin lesions are variable in size and are hairless, red, and scaly or crusty. In most dogs, the lesions are not itchy. The skin lesions seen in dermatomyositis are not unique to this disease. Dogs with ringworm, bacterial skin infection, demodectic mange, and discoid lupus, to name a few, can have similar lesions. No one can make the diagnosis of dermatomyositis or exclude that diagnosis simply by looking at the dog. Diagnostic tests must be performed. Skin biopsies are very important especially if the dog or any of its relatives are to be used for breeding.
   
   
7. Since the diseases has a genetic component, there is no cure for the disease. There are a variety of treatments which can help the dog. No treatment plan is best for all dogs and treatments must be individualized for each dog. Severely affected dogs are very problematic.
   
   
8. The genetic basis for the disease is unknown in the Sheltie. An autosomal dominant trait has been suggested but not proven by detailed breeding studies. These breeding studies must be done to develop that data.
   
   
9. ALL AFFECTED DOGS, REGARDLESS OF THE SEVERITY OF THEIR SKIN LESIONS, SHOULD NOT BE USED FOR BREEDING. Until the mode of inheritance is known, specific recommendations about breeding relatives of an affected dog can not be made.

Note especially points 8 and 9. Affected dogs: don't breed. Relatives of affected dogs: recommendations not possible without further research. Be cautious but not hysterical. Note also that there is no mention of DM being an autoimmune disease, very likely it is one of the "unknowns" about the disease.