- Affects puppies of collies and shetland sheepdogs from 8 weeks of age
- Lesions - vesiculating dermatitis
- Face, lips, external ears, later distal extremities
- Microscopically: interface dermatitis and basal cell degeneration of epidermis and follicular wall, atrophy of follicles, epidermal vesicles and pustules, dermal scarring
- Hereditary in Collies and Shetland sheepdgs
- Lesions resemble canine polymyositis
- Also degeneration of blood vessels -> muscle microinfarcts
- Usually generalised but temporalis and other masticatory muscles may be involved the most
- Microscopically: inclusion bodies in endothelial cells
- Best place for biopsy is anterior and most superficial temporalis muscle
- Also involves skin, may involve the oesophagus