A 2-year-old, female collie was presented with pigmented alopecia and scaly erythema at the face and over bony prominences. The lesions developed at 4 months of age. Histopathology of the skin lesions revealed hydropic degeneration of basal layers with mild monocytic infiltration. The dog was diagnosed as canine familial dermatomyositis based on the histopathology. Avoidance of sunlights, administration of antibiotics, vitamin E, niacinamide as well as occasional steroid seemed to be beneficial, although the lesions were exacerbated during estrus and summer season. The dog was moved and had been treated with systemic steroid administration at another local veterinary clinic. The dog was re-examined at 5 years old because of iatrogenic Cushing's syndrome. The lesions were improved with symptomatic therapies and withdrawal of steroids, though the dog died suddenly. Postmortem evaluations revealed degeneration and regeneration of myocardium and most skeletal muscles as well as glomerulonephritis.

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