SAD - Chapter 13 - Pigmentary Abnormalities

Question 1

Black and brown pigments are derived from what?

Answer 1

eumelanin

Question 2

Yellow and red pigments are derived from what?

Answer 2

pheomelanin

Question 3

T/F: Both hair and epidermal melanocytes are always active.

Answer 3

False - epidermal melanocytes are always active, but those in the hair are only active during anagen & their control and activity can change during hair growth

Question 4

T/F: Lighter skin has higher levels of melanosome degradation than darker skin.

Answer 4

TRUE

Question 5

Hyperpigmentation results from an increase in melanin in what layer of the skin?

Answer 5

epidermis and corneocytes

Question 6

achromotrichia

Answer 6

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

Question 7

Graying is due to what change within the hair?

Answer 7

decreased pigment of the hair

Question 8

leukoderma

Answer 8

lack of pigment in the skin

Question 9

leukotrichia

Answer 9

lack of pigment in the hair

Question 10

melanoderma

Answer 10

increased pigment of the skin

Question 11

melanotrichia

Answer 11

increased pigment of the hair

Question 12

poliosis

Answer 12

premature grayness of hair

Question 13

Macular melanosis that is intensely black with no known significance.

Answer 13

lentigo (lentigenes)

Question 14

Histopathological features of lentigines (lentigo)

Answer 14

increase in number of melanocytes and melanosomes, primarily in basal cell layer => over time, the epidermis may thicken, mild orthokeratotic hyperkeratosis may occur, slight rete ridge formation may be present

Question 15

Form of albinism seen in Siamese, Himalayan, Balinese, Burmese, and Singapura cats

Answer 15

acromelanism

Question 16

Why is the hair on the extremities of Siamese/Himalayan/Balinese/Burmese/Singapura cats pigmented?

Answer 16

temperature-sensitive hair bulb tyrosinase that is inactivated at warmer temperatures; therefore, extremities which are cooler are able to make pigment

Question 17

Melanotrichia has been reported to occur in dogs treated with what medication for Cushing’s disease?

Answer 17

o,p’-DDD (mitotane)

Question 18

Pigmented viral plaques are commonly reported in what breeds?

Answer 18

pugs, miniature schnauzer, Shar-Pei

Question 19

Pigmented viral plaques must be distinguished from what other condition in a young pug?

Answer 19

lentigo (lentigines)

Question 20

Fungal elements in the dermis often result in what color change? With what fungal diseases is this reported?

Answer 20

dark blue nodules or plaques due to melanin pigment within the fungus; phaeophyphomycosis

Question 21

melanocytopenic

Answer 21

absence of melanocytes

Question 22

melanopenic

Answer 22

decreased melanin

Question 23

_____ is a hereditary lack of pigmentation that is transmitted in an autosomal recessive trait and results in a mutation of the ____ gene.

Answer 23

Albinism; tyrosinase gene

Question 24

T/F: Animals with albinism lack melanocytes.

Answer 24

False - they have a normal number of melanocytes but they lack tyrosinase for melanin synthesis (and are unable to produce melanin)

Question 25

Genetically determined white spotting is known as what?

Answer 25

piebaldism

Question 26

T/F: Animals with Waardenburg-Klein Syndrome lack melanocytes.

Answer 26

True - the defect is in the migration and differentiation of melanocytes

Question 27

Mode of inheritance for albinism?

Answer 27

autosomal recessive

Question 28

Mode of inheritance for piebaldism?

Answer 28

autosomal dominant

Question 29

Mode of inheritance for Waardenburg-Klein Syndrome?

Answer 29

autosomal dominant

Question 30

Mode of inheritance of canine cyclic hematopoiesis?

Answer 30

lethal autosomal recessive

Question 31

Vitiligo results in leukoderma or leukotrichia through loss of what cell type?

Answer 31

melanocyte loss or destriction

Question 32

Aguirre syndrome - what is it? In what breed is it reported?

Answer 32

unilateral periocular depigmentation, Horner’s syndrome, corneal necrosis with uveitis, upper respiratory tract infections; Siamese cats

Question 33

Treatments for vitiligo

Answer 33

calcineurin inhibitors, vitamin D, antioxidants, narrow-band UVB light, amino acid L-phenylalanine

Question 34

Nasal hypopigmentation has been reported in what breeds? During what months?

Answer 34

Siberian huskies, golden retrievers, Labs, Bernese mountain dogs, typically in the winter months

Question 35

What phenotype can be expected in a Chow-Chow with a tyrosinase deficiency?

Answer 35

tongue is pink (instead of bluish black), portions of the hair shaft turn white, buccal mucosa may rapidly depigment

Question 36

What infectious disease can cause leukoderma without obvious swelling or infectious lesions?

Answer 36

leishmaniasis

Question 37

Loss of pigment on the nasal planum is commonly seen with what diseases?

Answer 37

mucocutaneous pyoderma, DLE, SLE, pemphigus erythematosus/foliaceus, UV syndrome, drug eruption, bullous pemphigoid, epitheliotropic lymphoma, SCC

Question 38

Diets deficient in what minerals and/or amino acids may result in red hair?

Answer 38

copper; phenylalanine and tyrosine

Question 39

What endocrinopathies can result in dark hair turning red or a lightening of the haircoat?

Answer 39

hypothyroidism, hypercortisolism, Sertoli cell tumors***

Question 40

What drugs can cause a reddish orange skin discoloration?

Answer 40

rifampin, beta-carotene, clofazimine