Chapter 12 - Pigmentary abnormalities

Question 1

What is missing in albinism?

Answer 1

Tyrosinase (needed for melanin synthesis)

Question 2

What are the signs of Waardenburg-Klein syndrome?

Answer 2

Blue/heterochromic eyes
Amelanotic skin and hair
Deafness

Question 3

Name two colour related lethal syndromes in foals

Answer 3

Lethal white foal syndrome

Coat color dilution lethal (lavender foal syndrome)

Question 4

Which breed of horse is vitiligo most common in?

Answer 4

Arabians (greys particularly)

Question 5

Leukoderma is often seen as a complication of which diseases?

Answer 5

Onchocerciasis 
Dourine
Herpes coital exanthema 
Lupus erythematosus
Pressure sores
Ear papillomas
Ventral midline dermatitis
Regressing viral papillomatosis
Freezing/burns
Contact with rubber (due to monobenzyl ether hydroquinone inhibition of melanogenesis?)

Question 6

What are the histopathological changes of early, crusted stages of reticulated leucotrichia?

Answer 6

Lichenoid interface dermatitis, apoptotic keratinocytes and satellite cell apoptosis, and superficial dermal edema and pigmentary incontinence. Intra- and subepidermal vesicles may be present.

Question 7

Which breeds of horse are over-represented with vitiligo?

Answer 7

Gelderlands
Spanish thoroughbreds
Arabians
Belgians

Question 8

What is the median age of onset of vitiligo in horses?

Answer 8

4 years

Question 9

Which body sites are most commonly affected by vitiligo in horses?

Answer 9

Head / face

Question 10

Where are lesions present with ‘spotted leukotrichia’ (well-circumscribed, small circular areas of near complete leukotrichia on otherwise normal skin) and which breeds of horse are more often affected?

Answer 10

Neck, trunk and rump

Thoroughbred, Shire and Arabians
possible variant of vitiligo