Pigmentary Abnormalities

Question 1

Pheomelanins are yellow and red pigments and contain cysteine thiol groups that react to form ________.

Answer 1

5-S-cysteinyl-dopa

Question 2

A variety of cytokines and leukotrienes influence melanocyte function, with leukotriene B4 locally stimulating, and IL-1, IL-6 and IL-7 inhibiting ______ in humans.

Answer 2

melanogenesis

Question 3

In contrast to epidermal melanocytes, which are always active, hair melanocytes are active only during _____, and their control and activity can change during hair growth.

Answer 3

anagen

**follicular melanocytes produce larger melanin granules

Question 4

Melanosomes larger than _______ are dispersed individually within keratinocytes, and smaller melanosomes are grouped into melanosome complexes.

Answer 4

0.5 to 0.7um

Question 5

In Border Collies, the incidence of deafness is associated with the _____ gene and the amount of white hair on the head.

Answer 5

merle

Question 6

It has been shown that cats deficient in _____ develop coat color changes and neurologic disease.

Answer 6

phenylalanine

Question 7

Achromotrichia

Answer 7

loss or absence of pigment in the hair; may be patterned; such as bands, or part of the hair shaft

Question 8

Graying

Answer 8

decreased pigment in the hair

Question 9

Poliosis

Answer 9

Premature grayness of the hair

Question 10

What is macular melanosis that is intensely black and usually occurs as multiple lesions that are most common the ventrum?

Answer 10

Lentigo

The hereditary form of this is called lentiginosis profusa and has been reported in pigs and was thought to an an autosomal dominant mode of inheritance.

Question 11

What is the histopathologic description of Lentigo?

Answer 11

early lesions are characterized by a sharply localized increase in the number of melanocytes and melanosomes. The epidermal pigmentation is greatly increased because almost every keratinocyte contains melanosomes.

Question 12

What is the syndrome that is characterized by asymptomatic macular melanosis usually beginning in cats younger than 1 year of age.

Answer 12

Lentigo Simplex in Orange Cats

Question 13

Define Nevi

Answer 13

Developmental defects of the skin and in some cases, have been hereditary in nature. They may have a relationship to dermatomes, Blasko lines or peripheral nerves and can appear in a linear fashion.

Question 14

What is a form of albinism that has been genetically selected for in Siamese, Himalayan, Balinese, Birman, Burmese and Singapura cats?

Answer 14

Feline Acromelanism

These cats have temperature-sensitive hair bulb tyrosinase that is activated at temperature of 35-37C. Therefore is the skin is cooled enough, such as normally on extremities or other areas following shaving, pigment production may occur in the hairs.

Question 15

Silver dogs are usually born with dark coats that lighten when the adult hairs develop. If melanotrichia is due to _____ influences, the hairs revert to their normal adult color at the next shedding. In other dogs, melanotrichia may be due to influences of melanocyte stimulating factors such as _____.

Answer 15

G-locus

LTB4

Question 16

________ and other pituitary lipotrophic hormones stimulate melanogenesis, and this factor may be why some hypercortisolism and adrenal sex hormone patients become hyper pigmented.

Answer 16

Corticotropin

Question 17

Treatment with what drug may be associated with hypermelanosis and melanotrichia?

Answer 17

mitotane (o,p’ DDD)

Question 18

Experimentally, what drug has been shown to cause hyperpigmentation,entation in dogs, and the effect was believed to be attributable to iron deposition?

Answer 18

minocycline

Question 19

What is the syndrome present for pigmented plaques that must be distinguish from lentigines? This disease is seen mainly in young pigs, miniature schnauzers and Shar Pets. Immunosuppresion can make other breeds more susceptible. Why is is important to distinguish between linguine’s and the other syndome?

Answer 19

Papillomavirus pigmented plaques

It is important to diagnose them since they are treatable and may develop into SCC.

Question 20

What fungal agent may develop dark blue nodules or plaques due to the melanin pigment within the fungus present in the dermis?

Answer 20

Phaeophyphomycosis

Question 21

What syndrome is an autosomal recessive disorder reported in Persian cats with yellow eyes ad a blue smoke hair coat color? It is characterized by partial oculocutaneous albinism.

Answer 21

Chediak Higashi Syndrome

Question 22

Albinism is a hereditary lack f pigmentation that is transmitted as an autosomal recessive trait and results in a mutation of the ____ gene. What two breeds of cats have their coat color as a result of mutations in this gene?

Answer 22

Tyrosinase gene
Siamese and Burmese

**Albino individuals have a normal complement of melanocytes, but they lack tyrosinase for melanin synthesis and thus have biochemical inability to produce melanin.

Question 23

Genetically determined white spotting is referred to as _______. It is common in dogs and is transmitted as completely DOMINANT trait. Melanocytes are absent or incompletely differentiated in affected sites.

Answer 23

Piebaldism

Question 24

What syndrome is associated with a defect in the migration and differentiation of melanoblasts. Therefore, the affected skin has no melanocytes present.

Answer 24

Waardenburg-Klein Syndrome has been described in cats, bull terriers, Sealyham terriers, collies and Dalmatians. In addition to blue eyes and melanotic skin/hair, the affected animals are dead and have blue or heterochromic irides.

Question 25

Canine cyclic hematopoiesis is a lethal autosomal ____ syndrome wherein collie puppies are born with silver-gray haricot that differs from the normal sable or tricolor coat. In some of these puppies, a slight yellow pigmentation may be present, which produced a picture of light beige and light gray hair.

Answer 25

recessive

Question 26

What is an acquired disease associated with melanocyte destruction, resulting in areas of leukoderma and/or leukotrichia?

Answer 26

Vitiligo

Question 27

Vitiligo is an uncommon disease and has a possible hereditary associated in what three breeds?

Answer 27

Tervuren, Rottweilers and Old English Sheepdogs

Question 28

Vitiligo has only been reported in one cat breed, which is?

Answer 28

Siamese

Question 29

What syndrome has been described in Siamese cats. This condition is associated with unilateral peropcular depigmentation, Horner syndrome, or corneal necrosis with uveitis and upper repertory tract infections.

Answer 29

Aguirre Syndrome

Question 30

Rottweilers have been seen to develop ___ and ____ concurrently with vitiligo.

Answer 30

onychomadesis and leukonychia

Question 31

The amino acid ______ has been used topically, systemically and in carious combinations with light therapy.

Answer 31

L-phenylalanine

Question 32

Hypopigmentation of the nose and lips is recognized in which two breeds? It is present from birth and is static.

Answer 32

Doberman Pinchers and Rottweilers

Question 33

Tyrosinase deficiency has been reported in what breed? It is very rare. The normally bluish black tongue turns pink

Answer 33

Chow Chows

This change in color is due to lack of tyrosine which is required to produce melanin. Melanin appears spontaneously in 2-4 months.

Question 34

What infectious disease in particular one must consider for leukoderma without obvious swelling or infectious lesions?

Answer 34

Leishmaniasis

Question 35

Some dogs that receive ____ for mycotic infections or ____ fir cardiac disease nat develop diffuse lightening of coat.

Answer 35

ketoconazole, Procainamide

Question 36

Deficiency of of what 4 nutrients will produce graying of the coat?

Answer 36

zinc, pyridoxine, pantothenic acid and lysine

Question 37

Diets deficient in what metal may cause red hair development in dogs?

Answer 37

Copper

Question 38

Cat diets deficient in aromatic amino acids, ______ and _____, result in black coats turning red.

Answer 38

phenylalanine and tyrosine

Question 39

Some dogs with what tumor fail to shed their coat normally, and hairs are actually retained in catagen or telogen. The hairs remain for years, the lightened, red, dry frizzy coat may be partly caused by chronic UC and environmental exposure.

Answer 39

Sertoli cell Tumors

Question 40

Paroxysmal flushing has been associated with what two neoplastic processes in dogs?

Answer 40

Pheochromocytoma

Mast cell tumors

Question 41

Lethal White Foal Syndrome

Answer 41

An autosomal recessive disorder resulting from the breeding of two overo spotted paint horses
Affected foals have a mutation in EdnrB causes abnormal or absence development and migration of neural crest cells that form melanocytes and enteric neurons
Affected foals are born white and apparently normal, but develop signs of colic due to an inability to pass feces
The foals lack myenteric plexuses and the involved intestine becomes contracted and atretic
They typically die between 1 and 5 days of age.

Question 42

Xanthophores and erythrophores

Answer 42

Chromatophores that contain large amounts of yellow pteridine pigments are named xanthophores and those with an excess of red/orange carotenoids termed erythrophores
It was discovered that pteridine and carotenoid containing vesicles are sometimes found within the same cell, and that the overall colour depends on the ratio of red and yellow pigments. Therefore, the distinction between these chromatophore types is essentially arbitrary.

Question 43

Waardenburg Syndrome

Answer 43

A hereditary syndrome characterized by varying degrees of deafness and facial bone defects and by variation in pigmentation of the skin, hair, or eyes.

Question 44

What are leucophores and iridophores

Answer 44

Iridophores, sometimes also called guanophores, are pigment cells that reflect light using plates of crystalline chemochromes made from guanine. When illuminated they generate iridescent colours because of the diffraction of light within the stacked plates. By using biochromes as coloured filters, iridophores create an optical effect known as Tyndall or Rayleigh scattering, producing bright blue or green colours.
Leucophore is found in some fish, particularly in the tapetum lucidum. Like iridophores, they utilize crystalline purines (often guanine) to reflect light. Unlike iridophores, however, leucophores have more organized crystals which reduce diffraction. As with xanthophores and erythrophores, in fish the distinction between iridophores and leucophores is not always obvious, but generally iridophores are considered to generate iridescent or metallic colours while leucophores produce reflective white hues.

Question 45

Type IV Waardenburg syndrome (Shah-Waardenburg syndrome)

Answer 45

3 different mutations of EdnrB gene have been implicated as a cause of this disease process
Additional defects to development of the distal aspect of enteric nervous system cells: aganglionosis of the colon

Question 46

What gene is mutated in lethal white foal syndrome?

Answer 46

a mutation in EdnrB

Question 47

Piebaldism

Answer 47

autosomal dominant disorder that results form mutations of c-Kit or SF (ET 3 is also implicated); leads to melanoblast failure to migrate to the skin and/or survive there
Humans: affected individuals display broad depigmented patches, most prominent on the central forehead and trunk; ventral aspect of the body is more frequently affected that the dorsal; rarely affects the melanocytes in the eyes or inner ear
Mice: complete absence of melanocytes as well as abnormalities of the reproductive and hematopoietic systems with homozygous loss of SF or c-Kit
Not recognized as an abnormality in domestic animals, as white spotting is widespread and well accepted