Page 1300 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Skin 1275

VetBooks.ir 12.75

Fig. 12.75 Equine Cushing’s
disease. Note the very long hair
coat. The tail and mane are
unaffected. (Photo courtesy
GA Munroe)

EQUINE CUSHING’S DISEASE

Definition/overview to a failure to shed body hair or rapid regrowth of
Horses with equine pituitary adenomas of the pars longer than normal hair (8–10 cm long) (Fig. 12.75).
intermedia clinically display signs of hirsutism due The mane and tail are not affected. (See also p. 916.)

IMMUNE-MEDIATED SKIN DISEASES

INTRODUCTION dermatopathologist are paramount to success in
reaching a diagnosis.
Inflammatory changes occur in the skin when it
is injured. These changes are initially related to CONTACT HYPERSENSITIVITY
the inciting cause and, secondarily, may relate to
autologous changes that follow the initial injury. Definition/overview
Protection of the host is by means of a structured Contact hypersensitivity is a rare and poorly docu-
immune response. In a normal response this action mented problem associated with skin contact with
is to restore normal body function, but under- or allergens, leading to a variable degree of pruritus and
overactivity often leads to serious problems for the maculopapular or lichenified dermatitis.
host. Under-response leads to infection and poor
elimination of toxic by-products. Over-response DRUG ERUPTION
gives an overabundant inflammatory response that
may result in the production of autoimmune disease. Definition/overview
Both these responses adversely affect the skin. Drugs, given by any route, including most antibiot-
Apart from insect hypersensitivity and urticaria, ics and many vaccines, may cause skin eruptions.
immune-mediated diseases in the horse are uncom-
mon to rare and their diagnosis may be aided by Aetiology/pathophysiology
elimination of all the other more common causes of The immune response is most commonly imme-
crusting and scaling. A very careful examination of diate but can also be delayed for weeks or even
the horse’s history, a series of careful chosen biopsies months after the initial administration of the
of recent primary lesions and the use of a veterinary causal drug.