SAD - Chapter 13 - Pigmentary Abnormalities Flashcards
Black and brown pigments are derived from what?
eumelanin
Yellow and red pigments are derived from what?
pheomelanin
T/F: Both hair and epidermal melanocytes are always active.
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
T/F: Lighter skin has higher levels of melanosome degradation than darker skin.
TRUE
Hyperpigmentation results from an increase in melanin in what layer of the skin?
epidermis and corneocytes
achromotrichia
loss or absence of pigment in hair; may be patterned, such as bands, or part of the hair shaft
Graying is due to what change within the hair?
decreased pigment of the hair
leukoderma
lack of pigment in the skin
leukotrichia
lack of pigment in the hair
melanoderma
increased pigment of the skin
melanotrichia
increased pigment of the hair
poliosis
premature grayness of hair
Macular melanosis that is intensely black with no known significance.
lentigo (lentigenes)
Histopathological features of lentigines (lentigo)
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
Form of albinism seen in Siamese, Himalayan, Balinese, Burmese, and Singapura cats
acromelanism
Why is the hair on the extremities of Siamese/Himalayan/Balinese/Burmese/Singapura cats pigmented?
temperature-sensitive hair bulb tyrosinase that is inactivated at warmer temperatures; therefore, extremities which are cooler are able to make pigment
Melanotrichia has been reported to occur in dogs treated with what medication for Cushing’s disease?
o,p’-DDD (mitotane)
Pigmented viral plaques are commonly reported in what breeds?
pugs, miniature schnauzer, Shar-Pei
Pigmented viral plaques must be distinguished from what other condition in a young pug?
lentigo (lentigines)
Fungal elements in the dermis often result in what color change? With what fungal diseases is this reported?
dark blue nodules or plaques due to melanin pigment within the fungus; phaeophyphomycosis
melanocytopenic
absence of melanocytes
melanopenic
decreased melanin
_____ is a hereditary lack of pigmentation that is transmitted in an autosomal recessive trait and results in a mutation of the ____ gene.
Albinism; tyrosinase gene
T/F: Animals with albinism lack melanocytes.
False - they have a normal number of melanocytes but they lack tyrosinase for melanin synthesis (and are unable to produce melanin)
Genetically determined white spotting is known as what?
piebaldism
T/F: Animals with Waardenburg-Klein Syndrome lack melanocytes.
True - the defect is in the migration and differentiation of melanocytes
Mode of inheritance for albinism?
autosomal recessive
Mode of inheritance for piebaldism?
autosomal dominant
Mode of inheritance for Waardenburg-Klein Syndrome?
autosomal dominant
Mode of inheritance of canine cyclic hematopoiesis?
lethal autosomal recessive
Vitiligo results in leukoderma or leukotrichia through loss of what cell type?
melanocyte loss or destriction
Aguirre syndrome - what is it? In what breed is it reported?
unilateral periocular depigmentation, Horner’s syndrome, corneal necrosis with uveitis, upper respiratory tract infections; Siamese cats
Treatments for vitiligo
calcineurin inhibitors, vitamin D, antioxidants, narrow-band UVB light, amino acid L-phenylalanine
Nasal hypopigmentation has been reported in what breeds? During what months?
Siberian huskies, golden retrievers, Labs, Bernese mountain dogs, typically in the winter months
What phenotype can be expected in a Chow-Chow with a tyrosinase deficiency?
tongue is pink (instead of bluish black), portions of the hair shaft turn white, buccal mucosa may rapidly depigment
What infectious disease can cause leukoderma without obvious swelling or infectious lesions?
leishmaniasis
Loss of pigment on the nasal planum is commonly seen with what diseases?
mucocutaneous pyoderma, DLE, SLE, pemphigus erythematosus/foliaceus, UV syndrome, drug eruption, bullous pemphigoid, epitheliotropic lymphoma, SCC
Diets deficient in what minerals and/or amino acids may result in red hair?
copper; phenylalanine and tyrosine
What endocrinopathies can result in dark hair turning red or a lightening of the haircoat?
hypothyroidism, hypercortisolism, Sertoli cell tumors***
What drugs can cause a reddish orange skin discoloration?
rifampin, beta-carotene, clofazimine
