Page 1227 - Veterinary Immunology, 10th Edition

corticosteroid treatment, but spontaneous hair regrowth also
VetBooks.ir occurs. Other autoimmune diseases that lead to hair loss include

pseudopelade. It differs from alopecia areata in the precise location
of the inflammatory infiltrate within the hair follicles. Likewise,

some cases of pemphigus vulgaris (see later) may also be restricted
to hair follicles.

Blistering Diseases

Blistering skin diseases have been described in humans, dogs,
horses, and cats. Known as the pemphigus complex, they are
classified according to the location of the lesions within the
epidermis. Some lesions develop deep within the epidermis. For
example, the most severe form (although very rare) is called

pemphigus vulgaris. In this disease, bullae (blisters) develop
around the mucocutaneous junctions, especially the nose, lips, eyes,
prepuce, and anus, on the tongue, and the inner surface of the ear.

These bullae rupture easily, leaving weeping, denuded areas that
may become secondarily infected. Histological examination of
intact bullae shows separation of the skin cells (acantholysis) in the
suprabasal region of the lower epidermis (Fig. 37.5). The
acantholysis results when autoantibodies destroy the desmosomes

that bind skin cells together. In pemphigus vulgaris, the
autoantigen is a desmosome protein called desmoglein-3. Binding
of antibodies to desmoglein-3 activates the proto-oncogene c-myc

and leads to keratinocyte proliferation. As a result, the
keratinocytes above the lesion proliferate and fail to express
adhesion proteins so that they separate from each other. Eventually
this leads to acantholysis and bulla formation.

1227