Pigmentary Abnormalities Flashcards
Pheomelanins are yellow and red pigments and contain cysteine thiol groups that react to form ________.
5-S-cysteinyl-dopa
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.
melanogenesis
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.
anagen
**follicular melanocytes produce larger melanin granules
Melanosomes larger than _______ are dispersed individually within keratinocytes, and smaller melanosomes are grouped into melanosome complexes.
0.5 to 0.7um
In Border Collies, the incidence of deafness is associated with the _____ gene and the amount of white hair on the head.
merle
It has been shown that cats deficient in _____ develop coat color changes and neurologic disease.
phenylalanine
Achromotrichia
loss or absence of pigment in the hair; may be patterned; such as bands, or part of the hair shaft
Graying
decreased pigment in the hair
Poliosis
Premature grayness of the hair
What is macular melanosis that is intensely black and usually occurs as multiple lesions that are most common the ventrum?
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.
What is the histopathologic description of Lentigo?
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.
What is the syndrome that is characterized by asymptomatic macular melanosis usually beginning in cats younger than 1 year of age.
Lentigo Simplex in Orange Cats
Define Nevi
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.
What is a form of albinism that has been genetically selected for in Siamese, Himalayan, Balinese, Birman, Burmese and Singapura cats?
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.
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 _____.
G-locus
LTB4
________ and other pituitary lipotrophic hormones stimulate melanogenesis, and this factor may be why some hypercortisolism and adrenal sex hormone patients become hyper pigmented.
Corticotropin
Treatment with what drug may be associated with hypermelanosis and melanotrichia?
mitotane (o,p’ DDD)
Experimentally, what drug has been shown to cause hyperpigmentation,entation in dogs, and the effect was believed to be attributable to iron deposition?
minocycline
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?
Papillomavirus pigmented plaques
It is important to diagnose them since they are treatable and may develop into SCC.
What fungal agent may develop dark blue nodules or plaques due to the melanin pigment within the fungus present in the dermis?
Phaeophyphomycosis
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.
Chediak Higashi Syndrome
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?
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.
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.
Piebaldism
What syndrome is associated with a defect in the migration and differentiation of melanoblasts. Therefore, the affected skin has no melanocytes present.
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.
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.
recessive
What is an acquired disease associated with melanocyte destruction, resulting in areas of leukoderma and/or leukotrichia?
Vitiligo
Vitiligo is an uncommon disease and has a possible hereditary associated in what three breeds?
Tervuren, Rottweilers and Old English Sheepdogs
Vitiligo has only been reported in one cat breed, which is?
Siamese
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.
Aguirre Syndrome
Rottweilers have been seen to develop ___ and ____ concurrently with vitiligo.
onychomadesis and leukonychia
The amino acid ______ has been used topically, systemically and in carious combinations with light therapy.
L-phenylalanine
Hypopigmentation of the nose and lips is recognized in which two breeds? It is present from birth and is static.
Doberman Pinchers and Rottweilers
Tyrosinase deficiency has been reported in what breed? It is very rare. The normally bluish black tongue turns pink
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.
What infectious disease in particular one must consider for leukoderma without obvious swelling or infectious lesions?
Leishmaniasis
Some dogs that receive ____ for mycotic infections or ____ fir cardiac disease nat develop diffuse lightening of coat.
ketoconazole, Procainamide
Deficiency of of what 4 nutrients will produce graying of the coat?
zinc, pyridoxine, pantothenic acid and lysine
Diets deficient in what metal may cause red hair development in dogs?
Copper
Cat diets deficient in aromatic amino acids, ______ and _____, result in black coats turning red.
phenylalanine and tyrosine
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.
Sertoli cell Tumors
Paroxysmal flushing has been associated with what two neoplastic processes in dogs?
Pheochromocytoma
Mast cell tumors
Lethal White Foal Syndrome
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.
Xanthophores and erythrophores
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.
Waardenburg Syndrome
A hereditary syndrome characterized by varying degrees of deafness and facial bone defects and by variation in pigmentation of the skin, hair, or eyes.
What are leucophores and iridophores
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.
Type IV Waardenburg syndrome (Shah-Waardenburg syndrome)
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
What gene is mutated in lethal white foal syndrome?
a mutation in EdnrB
Piebaldism
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
