Disease Ontology ID: DDTO:0000272

Disease Description: A disease affecting the skin and muscles, usually in collies or Shetland sheepdogs.

Inherit Mode: The trait is believed to be autosomal dominant with variable expressivity. This means that if either parent is affected, all puppies have a susceptibility to the disorder, but not all will be affected equally. The variability suggests there is more involved than simple inheritance, including internal factors such as the individual's immune system (also affected by heredity) and external factors (including possibly viral infection). The most severely affected dogs may be homozygous for the trait.

Disease Symptom: With this condition, the skin is almost alwaysaffected before, andworse than, muscle. Typically, skin lesions occur by 6 months of age.There is reddening,hair loss, blisters or small bumps, crusting and where severe,ulceration of the skin.Most often affected are the face (especially the muzzle and ear tips,and around theeyes), the tip of the tail, bony prominences (over the elbows forinstance) and the toes.Over time, the affected skin becomes scarred. The muscles are not always affected indermatomyositis, or theabnormalities may be so slight as to go unnoticed. When there ismuscle involvement, thepuppies may be weak and lethargic and have a slow rate of growth.Muscles (especially ofthe face and head) may appear smaller due to muscle atrophy (shrinkageand loss of use).The most severely affected dogs may have difficulty in chewing orswallowing. The legmuscles may also atrophy. The degree to which pups are affected variesconsiderably. Muscleinflammation is generally less severe in Shelties. Generally the clinical signs fluctuate over timefor no apparentreason, and many mildly affected dogs will outgrow the conditionbefore a year of age,although some may have permanent scars on their face or legs. Inseverely affected dogs,thecondition is progressive and these dogs may have to be euthanizeddue to severemuscle atrophy and associated problems such as an inability to eat anddrink properly,which may be complicated by pneumonia.

Disease Cause: -

Disease Diagnose: This disorder is usually suspected in a young collieor Sheltie withcrusting facial skin lesions, with or without muscle weakness. Thereare other conditionswhich can cause these types of lesions and your veterinarian will dotests such as a skinbiopsy to pinpoint the diagnosis. This is a simple procedure done withlocal anesthetic,in which your veterinarian removes a small sample of your dog's skinfor examination by aveterinary pathologist. The biopsy will show changes in the skinconsistent with thiscondition.

Treat Method: Skin lesions are exacerbated by trauma and byexposure toultraviolet light, so these should be avoided (by the use ofsunscreens for example). Thismay be all that is required in mildly affected dogs, who are likely tooutgrow thecondition with time. Dermatomyositis can usually be managed fairlywell in moderatelyaffected dogs, with the above precautions and the use of Vitamin E andoccasional use ofcorticosteroids for flare-ups. Your veterinarian will work with you todetermine how bestto manage the condition in your dog. Unfortunately, it is verydifficult to maintain thehealth and comfort of severely affected dogs, and euthanasia issometimes the best option. For the veterinarian: Pentoxifyllinemay help byimproving microvascular blood flow. A response may take 2 or 3months. Short term use ofglucocorticoids may be necessary for acute flare-ups of skin ormuscle inflammation, butlong term use should be avoided as it will exacerbate skin andmuscle atrophy.

Breeder Advice: Affected dogs should not be bred. Also, because itis difficult toidentify dogs that have only a mild form of this condition, closerelatives of affecteddogs (siblings and parents) should not be used for breeding. It isimportant toremember that because of the variation in expressivity, offspring ofonly mildly affecteddogs may have much more serious clinical signs.

Disease Description Source: Link