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Sarah - Mulller and Kirk > Chapter 11 - Alopecia and 13 - Pigment > Flashcards

Chapter 11 - Alopecia and 13 - Pigment Flashcards

1
Q

Which breed is most commonly affected by pattern baldness?

A

Dachshund

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2
Q

Which anatomical sites are most commonly affected by pattern baldness?

A

Convex pinnae, periaural, ventrum, caudal thighs

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3
Q

With pattern baldness, is epilation normal or abnormal?

A

Normal

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4
Q

Which histopathological feature can help distinguish pattern baldness from endocrine alopecia or alopecia areata?

A

Minaturised hair follicles are seen with pattern baldness

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5
Q

Which dog breeds are most commonly affected by flank alopecia?

A

Boxers > Airedales, English bulldogs, Schnauzers

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6
Q

With flank alopecia, what is the characteristic appearance of hair follicles on histopathology?

A

‘Witches feet’ appearance to hairs

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7
Q

In dogs, telogen effluvium is seen most commonly with which chemotherapeutic agent?

A

Doxorubicin

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8
Q

Ischaemic dermatitis is thought to occur with traction/compression alopecia, which drug may be beneficial?

A

Pentoxifylline

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9
Q

Which breeds are commonly affected with rabies vaccine alopecia?

A

Min./Toy Poodle, Maltese, small long-haired dogs

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10
Q

How long after rabies vaccination does alopecia occur?

A

2-4 months

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11
Q

What is erythema ab igne?

A

Chronic, radiant heat dermatitis from prolonged, repetitive exposure to heat

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12
Q

Which neoplasia is most often associated with paraneoplastic alopecia in cats?

A

Pancreatic neoplasia

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13
Q

What other characteristic clinical signs is seen with paraneoplastic alopecia in cats?

A

Shiny skin

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14
Q

What do you see on histopathology of exfoliative dermatitis and thymoma?

A

Hydropic interface dermatitis with some apoptosis

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15
Q

Which enzymes most notably affect melanin colour and production?

A

Tyrosinase and tyrosinase-related proteins 1 and 2

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16
Q

Define poliosis

A

Premature greyness of hair

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17
Q

Define achromotrichia

A

Loss/absence of hair pigment

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18
Q

Where are lentignes seen in dogs?

A

Ventrum

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19
Q

What causes colour point cats to have dark points?

A

Temperature sensitive hair bulb tyrosinase that is inactivated at 35-37^C

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20
Q

Which breeds are prone to post-inflammatory melanotrichia?

A

Yorkies, Silkies, Bedlingtons, Old English sheepdogs and Poodles

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21
Q

Albinism is due a to a mutation in which gene?

A

Tyrosinase gene (normal melanocytes but they lack the tyrosinase needed for melanin synthesis)

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22
Q

What is the phenotype of Waardenburg-Klein syndrome?

A

Amelonotic skin and hair, deafness, blue or heterochromic irides

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23
Q

With Waardenburg-Klein syndrome, how does the genetic defect affect melanocytes?

A

Defect in migration and differentiation of melanoblasts which leads to no melanocytes

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24
Q

Which hair colour has the highest nutritional requirement for production?

A

Black

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25
Q

In which breed of cat is vitiligo reported?

A

Siamese

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26
Q

Which infectious disease can cause leukoderma in the absence of overt swelling or other lesions?

A

Leishmaniasis

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27
Q

Pinnal erythema in cats has been associated with administration of which antibiotics?

A

Enrofloxacin and ciprofloxacin

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28
Q

At which body site do vitiligo lesions initially develop in dogs?

A

Depigmented macules and/or patches initially developed on the face and were more often multifocal than focal. The gingiva and lips were the two most commonly affected regions.

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29
Q

Is dermal depigmentation present in the rare form of follicular vitiligo in dogs?

A

No - leukotrichia without leukoderma

Reported in Labrador retriever puppies

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30
Q

Is there a facial predominant form of vitiligo in horses and cats as in dogs?

A

Yes - although case reports are low in number

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31
Q

What are the key histopathological features of vitiligo?

A
  • Loss of melanocytes from the epidermis and/or hair follicle.
  • The epidermal architecture is normally retained but keratinocytes lack melanosomes in fully developed areas.
  • Melanosomes are spilled to the superficial dermis (pigmentary incontinence), and sometimes the hair follicle peribulbar area, where they are incorporated in melanophages.
32
Q

Where are lymphocytes found in vitiligo?

A

Minimal-to-mild numbers of lymphocytes are often present in the basal epidermal layer, especially near the junction of pigmented and nonpigmented epidermis; here lymphocytes are rarely observed adjacent to apoptotic melanocytes (“satellitosis”).

33
Q

Melanocytes of the vertebrate integument are _____ cells of neural crest cell origin

A

dendritic

34
Q

Melanin synthesis results in the generation of hydrogen peroxide and _______ intermediates which, if inappropriately processed, can damage the cellular components of epidermal melanocytes.

A

quinone

35
Q

Name three factors known to regulate the quantity and quality of melanins produced by melanocytes

A

UV radiation
alpha-MSH
Agouti signal protein

36
Q

Does alpha-MSH induce eumelanin or pheomelanin synthesis?

A

Eumelanin

Agouti signal protein induces pheomelanin

37
Q

alpha-MSH binds to which receptor on melanocytes?

A

MSH receptor (MSH-R), also known as melanocortin 1 receptor (MCR-1)

Agouti signal protein acts as a competitive antagonist of α-MSH for the MSH-R

38
Q

During its development, the melanosome acquires three gene-related melanogenic metalloenzymes, tyrosinase, and what else?

A

Tyrosinase-related protein 1 (Trp1) and and 2 (Trp2)

Tyrosinase is the most critical to melanogenesis!

39
Q

Which mineral is essential for tyrosinase activity?

A

Copper

40
Q

What is the is the metabolic precursor of melanin?

A

L-tyrosine (amino acid)

41
Q

α-MSH is produced in melanocytes and which other epidermal cell?

A

Langerhans cells

42
Q

Apart from alpha-MSH which other hormone can bind to MSH receptors in melanocytes and induce eumelanogenesis?

A

ACTH

Both enhance melanocyte proliferation, melanogenesis and melanocyte dendrite formation

43
Q

How is melanin photoprotective?

A

It directly absorbs ultraviolet photons and reactive oxygen species (ROS) generated by the interaction of ultraviolet photons with membrane lipids and other cellular chromophores

44
Q

Which breeds of dog are predisposed/commonly reported with vitiligo?

A

Rottweiler
Doberman pinscher dogs
Collies
Belgian Tervuerens

45
Q

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

A

2 years

46
Q

At which body site do cats develop lesions of vitiligo?

A

Nasal planum
Periocular
Footpads

47
Q

Name the disease

arrow heads = lymphocytes

A

Vitiligo

Arrow = melanophages

48
Q

Does vitiligo spontaneously resolve?

A

Yes - in some cases

49
Q

Tham et al. (2019); which treatments should be used for vitiligo in dogs?

A
  1. Topical high potency steroids
  2. Tacrolimus
  3. Oral L-tyrosinase supplementation for 6 months
    (4. NB-UVB Phototherapy may be promising option)
    Do not guarantee repigmentation!
50
Q

Which genes were found to be upregulated in vitiligo and VKH/UDS in dogs?

A

IFNG, TNF, PRF1, IL15, CTSW, CXCL10, and CCL5

51
Q

Dog leukocyte haplotype (DLA)-DQA1*0020 has been associated with which disease?

A

Uveodermatological syndrome in American Akitas

52
Q

Which breeds of dog are over-represented with UDS?

A

Akitas, Samoyeds and Siberian Huskies

53
Q

What is the typical age and sex of dogs affected with UDS?

A

3.6 years

Males > females

54
Q

Do ocular or cutaneous signs develop first in dogs with UDS?

A

Ocular in 85%

86% of dogs will have both within 6 months

55
Q

What are the non-cutaneous signs of UDS?

A
  1. Blindness or poor/decreased vision 56%
  2. Uveitis 40%
  3. Conjunctivitis 18%
    Lethargy, head tilt, reduced appetite, pica
56
Q

Other than leukoderma and leukotrichia, what cutaneous signs have been reported in dogs with UDS?

A
  • Erosions-ulcerations
  • Alopecia
  • Erythema
  • Swelling of the nose (loss of architecture)
  • Pruritus
  • Hyperkeratosis of footpads
  • Onychomadesis (loss of claws)
57
Q

What is the distribution of skin lesions in dogs with UDS?

A
  1. Nasal planum 86%
  2. Periorbital skin/eyelids 74%
  3. Lips 65%
  4. Mouth/oral cavity, footpads and/or the genitalia (males) 23%
58
Q

What are the histopath findings in canine UDS?

A
  1. Superficial perivascular inflammation that coalesces into lichenoid pattern that includes macrophages, lymphocytes, plasma cells and a variable number of neutrophils
  2. Exocytosis of lymphocytes into the lower epidermis blurs dermo-epidermal junction, but basal keratinocyte injury and loss is limited or absent.
  3. There is partial-to-complete loss of melanocytes
  4. Pigmentary incontinence
  5. Epidermal hyperplasia is normally seen with erosions, ulcers, neutrophil transmigration, patchy parakeratosis and/or crusting
59
Q

Does initiating treatment within 1 month of the first clinical signs of UDS in dogs affect outcome?

A

Yes - early treatment = better outcome

60
Q

Tham et al. (2019); what is the recommended treatment for UDS in dogs?

A
  1. Topical ophthalmic together with systemic GC at 2 mg/kg/day or higher.
  2. Other immunosuppressive therapies, such as azathioprine or ciclosporin, should be added if GCs therapy fail to induce the CR of signs
61
Q

How do you describe the lesions of lentigo?

A

Macular melanosis

62
Q

At what age do dogs develop lentigines and how do they progress?

A

Mature age

Develop in number and size over a few months then remain static

63
Q

What is a differential for macular melanosis if the skin feels rough or thickened?

A

Epidermal nevi

Papilloma virus induced lesions (viral plaques)

64
Q

At what age do cats develop lentigo?

A

<12 m

65
Q

When do you see post-inflammatory melanotrichia (in Yorkshire terriers, silky terriers, Bedlingtons, OES and poodles)?

A

After healing of deep inflammation e.g. panniculitis, vaccine reactions, wounds, sebaceous adenitis (poodles)

66
Q

A patch or plaque of grey-blue comedones should raise suspicion for which disease?

A

Demodicosis

67
Q

Which drugs have been associated with hyperpigmentation reactions in dogs?

A

Ketoconazole

Minocycline

68
Q

‘Snow nose’ occurs in which breeds of dog?

= decreased pigmentation of the nose in the winter (can be cyclic)

A

Siberian huskies
Golden retrievers
Labradors
BMDs

69
Q

Mucocutaneous hypopigmentation can be seen in Dobermans and Rottweilers, how doses it differ from vitiligo?

A

It is present from birth and is static in nature

70
Q

A temporary loss of pigment in Chow puppies that spontaneously resolves in 2-4 months is associated with a deficiency of which enzyme?

A

Tyrosinase

71
Q

Acquired hypopigmentation of the nose and lips can occur in dogs after contact with what?

A

Rubber/plastic food bowls

72
Q

Which drugs have been associated with hypomelanosis?

A 
S/C injections and topical GCs
S/C progestational drugs 
Ketoconazole
Procainamide 
Potent antioxidants (dihydroquinone) 
Cabergoline
73
Q

Reddish discolouration of the hair coat can be seen with which endocrinopathies?

A

Sertoli cell tumours and hyperoestrogenism > hypothyroidism and HAC

74
Q

Which drugs have been reported to cause colour change to the skin?

A

Clofamizine - cat, red/orange

Enro-/ciprofloxacin - cat, pinnal erythema

75
Q

Can melatonin implants prevent recurrence of seasonal flank alopecia in dogs?

A

No

Sarah - Mulller and Kirk (14 decks)

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