CHAPTER 20 DERMATOMYOSITIS, CANINE FAMILIAL 313
Moderate disease: lesions may persist for 6 months or more.
Severe disease: lesions usually persist throughout life and become progressive.
Adult-onset disease: much less common.
RISK/AGGRAVATING FACTORS
Trauma
Sunlight
Estrus
Parturition
Lactation
CLINICAL FEATURES
The clinical signs vary from subtle skin lesions and subclinical myositis to severe skin
lesions and generalized muscle atrophy.
Waxing and waning skin lesions particularly in areas of trauma/pressure: in dogs
<6 months old; around the eyes, lips, face, inner ear pinnae, tail tip, and bony
prominences of distal extremities; healing may lead to residual scarring and pigment
changes; primary vesicular lesions are rare; ulceration can occur in severe cases.Muscle atrophy of the masseter and/or temporal muscles may be evident.
Severe cases may exhibit difficulty eating, drinking, and swallowing; stunted growth;
gait abnormalities; widespread muscle atrophy and infertility.
Littermates may be affected; severity of the disease varies significantly among affected
dogs.
Skin lesions: characterized by papules and vesicles (rare); variable degrees of ery-
thema; alopecia, scaling, crusting, ulceration, and scarring on the face with pigmen-
tary changes, around the lips and eyes, in the inner ear pinnae, on the tail tip, and
over bony prominences on the distal extremities (Figures 20.1–20.5).Footpad and oral ulcers rare.
Myositis: variable; from nonclinical to a bilateral symmetric decrease in the mass of
the temporalis muscles to generalized symmetric muscle atrophy; lameness.
Aspiration pneumonia: secondary to megaesophagus.
DIFFERENTIAL DIAGNOSIS
Demodicosis
Dermatophytosis
Bacterial folliculitis
Juvenile cellulitis
Cutaneous lupus erythematosus
Systemic lupus erythematosus
Polymyositis