Page 1247 - Veterinary Immunology, 10th Edition

VetBooks.ir Dermatomyositis

A familial disease of dogs that resembles dermatomyositis in
humans has been described in Collies and Shetland Sheepdogs. It is

a complement-mediated microangiopathy in which complement-
mediated vascular damage leads to muscle ischemia. The disease is
inherited as an autosomal dominant involving a locus on
chromosome 35, although expression is highly variable. A similar
dermatomyositis-like disease has been described in other breeds

such as Pembroke Welsh Corgi, Lakeland Terrier, Chow, Jack
Russell Terrier, German Shepherd, and Rottweilers. Dogs develop
dermatitis with a less obvious myositis. Puppies appear normal at

birth, but skin lesions develop between 7 and 11 weeks of age, and
myositis develops between 12 and 23 weeks. In other studies, the
dermatitis developed at 3 to 6 months of age, and myositis was
detected after the dermatitis was investigated. The dermatitis first
develops on the face; subsequently, lesions may spread to the limbs

and trunk, especially over bony prominences. These early lesions
are erythematous and eventually lead to vesicle and pustule
formation. There is diffuse hair follicle atrophy and keratinocyte

degeneration that can lead to ulceration (Fig. 37.11). Once the
vesicles rupture, they ulcerate and crust. Lesions may be found on
the bridge of the nose and around the eyes and show hair loss and
changes in pigmentation. There may be local lymph node
enlargement. The clinical course and severity are variable, but skin

lesions usually resolve by 1 year of age.

1247