Page 1259 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1234 CHAPTER 12

VetBooks.ir ALOPECIC CONDITIONS

Alopecia is deficiency of the hair caused by fail-
ure to grow or loss after growth, and arises from a PRIMARY ALOPECIA
variety of primary and secondary diseases. There PHYSICAL BURNS
is a significant difference between those condi-
tions in which grown hairs are lost, those in which See Chapter 13 (p. 1318).
stumps of hairs remain and those in which the
hair root has been shed from the follicle. The pri- SET-FAST
mary change is loss of hair and this may be accom-
panied by, or caused by, pruritus as a primary Definition/overview
condition. Areas of superficial gangrene develop from persis-
Superficial changes such as scaling and crust- tent chronic pressure caused by a poorly fitting sad-
ing can progress to erosion and ulceration of the dle or other harness.
epidermis and dermis, and may accompany alope-
cia. Scaling, either dry or greasy, is due to shed- Aetiology/pathophysiology
ding of dead epidermal cells, while crusting is a External pressure on the skin causes vascular dam-
collection of variously coloured skin exudates. age and tissue anoxia and, if prolonged, dry gangrene
It may be possible during the preliminary exami- and/or skin slough.
nation to determine whether a physical, chemi-
cal or infectious agent may be involved, allowing Clinical presentation
a subdivision into these categories, but clinical Set-fast is characterised by roughly circular areas
signs of scales and crusts are not diagnostic in of skin that initially may be raised and painful, due
themselves. to progressive damage, which eventually leads to
Erosion and ulceration are both secondary a cardboard-like consistency of the affected skin
changes. Erosions are associated with loss of epi- (Fig. 12.23).
dermis at varying levels down to the basement
membrane, and these lesions heal without scarring. Diagnosis
Ulceration damages tissue beyond the basement History and lesion location are used for diagnosis.
membrane and may result in scarring and alopecia.
Additional information will allow some further divi- Management
sion into physical and chemical causes, infectious Saddlery should be examined and any improperly
agents, tumours (or nodules), immune-mediated dis- fitting areas corrected. The horse should be rested.
eases and miscellaneous diseases. Early cases can be treated with astringents and
massage. Old cases may require surgery and skin
grafting.
12.23
Prognosis
The prognosis is good with treatment for early dam-
age. Surgical results following prolonged injury
are fair.

URINE SCALDING
Fig. 12.23 ‘Set-fast’. The withers region of this
horse became swollen and sore, with a dried out Definition/overview
‘cardboard’-like skin, due to pressure necrosis from a Urine scalding is usually found around the skin of
poorly fitted saddle. the caudal area of the hindlimbs of mares and the