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Vet Derm Review > Structure and Function - hair follicles > Flashcards

Structure and Function - hair follicles Flashcards

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1
Q

What effect does substance P have on the hair cycle?

A

anti-proliferative and pro-apoptotic effects: abrupt cessation of anagen, increased apoptosis in hair follicle resulting in premature catagen, increased perifollicular macrophage clusters, incrreased mast cell degranulation

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2
Q

What effect does ACTH have on the hair cycle?

A

causes mast cell degranulation, activates hair growth in telogen skin, also induces premature transition to catagen

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3
Q

What is the “permanent” portion of the hair follicle?

A

isthmus and infundibulum

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4
Q

What is the predominant inflammatory cell associated with alopecia areata?

A

Cd8+ T cell lymphocytes in the bulb – CD4+ T cells in the peribulbar region

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5
Q

What is the role of KGF (keratinocyte growth factor) in the hair cycle?

A

promotes anagen; produced by anagen dermal papilla –> important for hair growth and cycling

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6
Q

Describe the changes that take place during early catagen (I-IV)

A

Dermal papilla moves upward, mitotic activity stops, apoptotic keratinocytes, pigmentation stops, trailing connective tissue sheath visible

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7
Q

What is the mutation in hairless Sphynx cats?

A

keratin 71 gene – keratin 71 is a type II keratin expressed throughout the IRS in mice and humans –> important for molding the hair shaft

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8
Q

What is immediate telogen release?

A

shortening of the normal telogen phase with exogen as follicles are stimulated to re-enter anagen (terminates telogen retention)

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9
Q

T/F: The number of hairs is reduced with follicular dysplasia.

A

False - normal number of hairs but hairs have structural changes –> hairs are fragile and malformed

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10
Q

Clinical presentation of mural mucinotic isthmus folliculitis of Lundehunds?

A

multifocal, patchy alopecia (may wax and wane); scaling, comedones, follicular casts; mild to severe pruritus; thorax, face and/or distal limbs most often affected

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11
Q

Exogenous factors that lead to initiation of anagen

A

TSH, T3/T4, day length

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12
Q

What effect do thyroid hormones have on the hair cycle

A

accelerate follicular activity; T4 upregulates human hair matrix keratinocytes; T3 and T4 down-regulate apoptosis, preventing catagen; T3 and T4 prolong anagen in vitro (via downregulation of TGF-beta –> inhibits anagen); anagen shortened*

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13
Q

T/F: Sphynx cats with the Hr mutation lack whiskers.

A

False - they have whiskers, but are short and curled

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14
Q

What are the two types of color-linked follicular dysplasias?

A

color dilution alopecia, black hair follicular dysplasia

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15
Q

What transcription factor is important for follicle induction?

A

Lef-1

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16
Q

What effect does promoting the wingless (wnt) signlaling pathway have?

A

new hair follicle induction

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17
Q

Poorly pigmented hairs characteristic of the prenatal period

A

Lanugo hairs

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18
Q

Describe the changes that take place during late anagen (IIIc-VI)

A

dermal papilla fully enclosed, DP in SQ, hair reaches surface, loss of club hair

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19
Q

Describe changes associated with Naked Foal Syndrome

A

Hypotrichosis and mild/moderate ichthyosis, nearly complete alopecia, vibrissae distorted**, die at a young age

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20
Q

Regions of the scalp (humans) that do not experience androgenic balding are higher in what enzyme involved in androgen pathways?

A

aromatase –> converts testosterone to estradiol in these follicles

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21
Q

Where does the outer root sheath keratinize?

A

level of isthmus – via trichilemmal keratinization

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22
Q

What effect does BMP-4 (bone morphogenic protein) have on Sonic hedgehog (Shh) and Wingless (Wnt) signaling?

A

inhibits their signaling –> inhibts hair growth

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23
Q

Histopathologic findings with alopecia areata

A

lymphocytic inflammation around and within the hair bulb; miniaturization of hair follicles below the sebaceous gland, pigmentary incontinence in the peribulbar region; peribulbar fibrosis (“onion skinning”), eosinophilic hair shafts, infundibular hyperkeratosis

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24
Q

T/F: Nail changes are possible with alopecia areata.

A

True - as well as hoof abnormalities in horses

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25
Q

What is the major component of the hair shaft?

A

Keratins (keratin intermediate filaments)

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26
Q

T/F: The hair shaft has no attachment to the infundibulum or isthmus.

A

True

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27
Q

What breeds are associated with post-natal ectodermal dysplasia? What is phenotype?

A

Pattern baldness: Portugese Water dog, Curly-coated retriever, Chesapeak Bay Retriever, Bald thigh syndrome in Greyhounds, etc.

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28
Q

Exogenous factors that lead to premature catagen induction

A

glucocorticoids, estrogen, substance P, NGF, TGF-beta-2

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29
Q

Possible pathomechanisms of post-clipping alopecia

A

clipping at early telogen stage –> hair regrowth delayed; time of year, geographic region; vascular perfusion changes in response to altered cutaneous temperature

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30
Q

Describe the isthmus of the hair follicle

A

proximal end of the infundibulum to the interface between the completely cornified IRS and the first non-cornifed cell of the Huxley’s layer (=Adamson’s fringe; approximately the insertion of the arrector pili muscle). Contains the HF stem cells

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31
Q

T/F: Exogen is a passive process where the new hair “pushes out” the old hair.

A

False - active process, involving proteolysis of intercellular adhesion molecules between the club hair and the surrounding epithelium

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32
Q

What produces the trichilemmal cornification?

A

outer root sheath

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33
Q

Mode of inheritance of naked foal syndrome? What breed is affected?

A

autosomal recessive (monogenic = ST14 gene) - -Akhal-Teke horses

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34
Q

What is the role of sonic hedgehog signaling in the hair cycle?

A

critical for induction of anagen; critical for hair follicle morphogenesis

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35
Q

T/F: Hair cycle arrest disorders cannot be differentiated on histopathology.

A

True - no features consistently differentiate them – all have increased kenogen follicles (likely that anagen is not being induced)

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36
Q

Mode of inheritance of hairless genotype in Xolo dogs?

A

autosomal dominant

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37
Q

Color-linked follicular dysplasias have been linked to what gene in some dog breeds?

A

melanophilin

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38
Q

Describe changes associated with X-linked anhidrotic/hypohidrotic ectodermal dysplasia

A

alopecia at birth; dentition changes - partial adontia, malformation, malposition; no glands are affected

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39
Q

What is the clinical presentation of proliferatve, lymphocytic, infundibular mural folliculitis with apoptosis and parakeratotic casts (PLIMF)?

A

only reported in Labrador retrievers, All dogs were female, median age of onset 6 years; Clinical signs: Thick, greyish-brown, adherent, hyperkeratotic plaques; variable alopecia; comedones in early lesions

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40
Q

What are the reported triggers of granulomatous mural folliculitis?

A

viral (caprine- and ovine-herpesvirus-2 – deer and goat), drugs (methimazole in a cat, various in the dog), or idiopathic

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41
Q

T/F: Intact females can show signs of Cushing’s disease due to activation of glucocorticoid receptors by progesterone.

A

False - even though progesterone DOES bind to the glucocorticoid receptor, intact females do not show cushingoid signs during their cycle

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42
Q

T/F: Dogs have androgen-responsive follicles.

A

False - do not grow hair in the presence of testosterone, do not lose hair in response to testosterone

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43
Q

What is chronic telogen defluxion?

A

increased telogen hair shedding occurring for 6 months or more (diagnosis made after ruling out other causes of hair loss)

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44
Q

T/F: Additional ectodermal defects may exist in combination with follicular dysplasia.

A

True - in people it is classified as a primary defect in at least two of the following: hair, teeth, nails, sweat glands

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45
Q

What has been shown to cause immediate telogen release?

A

minoxidil and response to rapid light/dark fluctuations

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46
Q

What effect do corticosteroids have on the hair cycle?

A

suppress anagen and catagen, including trauma-induced anagen; block keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF); inhibits local IGF-1 production (stimulant of anagen); may also have effects on the estrogen receptors; Anagen shortened –> miniaturization and atrophy

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47
Q

T/F: Hair grows faster in the morning.

A

True - the circadian clock generates a daily mitotic rhythm –> radiation causes more hair loss when administered in the morning during the mitotic peak

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48
Q

What effect does estrogen have on BMP-4 (bone morphogenic protein)? What effect does this have on the hair cycle?

A

estrogen activates BMP-4 –> leads to inhibition of hair growth (dowregulates Shh, Wnt1 signaling)

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49
Q

T/F: Sphynx cats with the Hr mutation are hairless.

A

False - they have short fine hairs protruding from the follicular ostia with reduced diameter; hair is often curved and may have kinks, tufts of short hair on the ears, muzzle, tail, feet, and scrotum, whiskers are short and curled.

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50
Q

Histologic changes of hair cycle arrest disorders

A

hyperkeratosis, follicular dilation, follicular atrophy, telogen hairs, kenogen hairs ***, epidermal melanosis, epidermal atrophy

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51
Q

Exogenous factors that can inhibit anagen onset

A

glucocorticoids, estrogen, testosterone, BMP-4, IL-6, stress

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52
Q

Clinical presentation of feline proliferative and necrotizing otitis and dermatitis

A

Kittens and adult cats (median age = 1.75 years); hyperkeratotic, crusty, proliferative, firmly adherent plaques with or without erosions and ulceration - found on concave aspect of pinna and ear canals; lesions may also affect muzzle and paws; pain or pruritus seen

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53
Q

During what phase of the hair cycle does hair pigmentation occur?

A

anagen – melanosomes migrate and are transferred into hair matrix

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54
Q

From what embryonic tissue is the dermis formed?

A

mesoderm (composed of mesenchymal cells)

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55
Q

The coat type of cats is determined by genetic variants of what three genes?

A

KRT71 (keratin 71) = hairlessness in Sphynx, Curly coat in Devon Rex and Selkirk Rex; LPAR6=Curly coat in Cornish Rex and German Rex; FGF5 (fibroblast growth factor-5) = Long hair

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56
Q

Differences between adult coat and puppy coat

A

Adult coat develops secondary hairs, increased number of hair shafts, increased diameter of hair shafts, decrease in curvature of hair shaft

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57
Q

Histologic features of color-linked follicular dysplasias?

A

abnormal melanin clumping within hair cortex, medulla, bulb and periadnexally; hyperkeratosis and follicular keratosis

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58
Q

What is the Huxley layer?

A

part of the inner root sheath, 2-4 layers thick, keratinizes above Henle at the region known as Adamson fringe (keratogenous zone)

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59
Q

Mode of inheritance of hairless genotype in Sphynx cats?

A

autosomal recessive

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60
Q

T/F: Estrogens are essential for normal hair growth.

A

False - OVH does not significantly alter the coat

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61
Q

Clinical presentation of feline degenerative mucinotic mural folliculitis

A

generalized, progressive alopecia with scaling and crusting; leions first often presented on the face or neck; +/- pruritus; swollen face – especially the muzzle (all cases)

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62
Q

Exogenous factors that can lead to induction of exogen

A

stress, minoxidil

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63
Q

Clinical signs of alopecia areata

A

multifocal, well-demarcated patches of alopecia; leukotrichia; face most commonly affected; loss of eyelashes and whiskers possible; nail changes possible - trachyonchyia (sand paper nails with fine longitudinal ridges)

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64
Q

Describe the suprabulbar region of the hair follicle

A

Presence of a not yet fully cornified IRS characterized by trichohyalin granules in the cytoplasm of the cells

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65
Q

T/F: Follicular dysplasia of Weimaraners is more severe than other color dilution phenotypes.

A

False - similar to color dilution but less severe

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66
Q

Histologic changes with follicular dysplasia of Weimaraners

A

increased size and number of melanin aggregates; crater defects of hair shaft; dermal melanophages seen less frequently

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67
Q

Poorly pigmented hairs in people typical of fine hairs on face and arms

A

Vellus hairs

68
Q

Exogenous factors that lead to prolonged anagen

A

TSH, T3/T4, Cyclosporine A, caffeine

69
Q

Describe features of follicular lipidosis

A

develops in first few months of life; breed-specific: Rottweilers and a Dachshund dog; affects mahogany-colored hair on feet and face; associated with lipid vacuoles within cells of hair follicle matrix

70
Q

Describe the changes that take place during telogen

A

hair follicle an dermal papilla in dermis; club hair firmly anchored; no inner root sheath; no trailing connective tissue sheath

71
Q

When does exogen happen?

A

late anagen to early telogen - depends on the hair type and species

72
Q

What two forms of cutaneous lupus erythematosus show lymphocytic interface and mural folliculitis, affecting the infundibulum and isthmus? What other histopathologic changes can be found?

A

generalized discoid lupus erythematosus and exfoliative cutaneous lupus erythematosus; hair follicle and sebaceous gland atrophy have been reported as well

73
Q

The coat type of most dogs is determined by genetic variants of what three genes?

A

RSPO2 (encoding R-spondin-2), FGF5 (fibroblast growth factor-5), KRT71 (keratin 71)

74
Q

What is unique about the hair follicles of Llamas?

A

Simple follicles, but may have new anagen hair and old telogen hair occupying the same follicle

75
Q

What products can increase insulin-like growth factor 1 locally?

A

cepharanthine and capsaicin (substance P antagonist)

76
Q

What are the 3 mechanisms by which a thymoma can predispose animals to autoimmune disease?

A

1) Escape of thymoma-driven thymocytes into periphery w/o critical selection; 2) increased proliferation of thymocytes with an aberrant TCR expression; 3) Mutation in HLA Class II genes, resulting in a defective education of thymocytes by thymic epithelial cells

77
Q

What are examples of post-natal neuroectodermal dysplasia?

A

color dilution alopecia, black hair follicular dysplasia, follicular lipidosis

78
Q

During what phase of melanogenesis is the defect in color-linked follicular dysplasias?

A

defect in melanosome migration/transfer (neuroectodermal defect)

79
Q

Skin lesions with granulomatous mural folliculitis

A

patchy to diffuse alopecia with variable degree of erythema and scaling

80
Q

What breeds of horses are over-represented with alopecia areata

A

Appaloosa, American saddlebred, Peru paso

81
Q

Mode of inheritance of hairless genotype in Chinese crested dogs?

A

autosomal dominant

82
Q

T/F: Non-thymoma-associated exfoliative dermatitis responds well to medical therap.

A

True - 67% response rate reported - drugs used included glucocorticoids +/- cyclosporine

83
Q

Compound hair follicles are seen in what species?

A

dogs, cats, other carnivores, and rabbits**

84
Q

What are the layers of the hair shaft? Which layer is the bulk of the mass of the hair shaft?

A

cuticle, cortex, medulla; cortex is the bulk of the fiber mass and accounts for the tensile strength of the hair shaft

85
Q

When are primary hairs shed? Secondary hairs?

A

Primary hairs are shed all year round; Secondary hairs are shed seasonally**

86
Q

Describe the skin and hair of Chinese crested dogs with the Hr mutation

A

Follicles are simple, deformed, dysplastic; comedones with remnants of dermal papilla at the base of the follicle; normal functioning sebaceous and sweat glands

87
Q

Histopathologic findings with thymoma-associated exfoliative dermatitis

A

cell-poor to cell-rich lymphocytic interface dermatitis - and mural folliculitis (infundibulum +/- isthmus), trans-epidermal apoptosis, prominent hyperkeratosis due to sebaceous adenitis or loss of sebaceous glands (Lupus + EM + sebaceous adenitis)

88
Q

What is the Henle layer?

A

part of the inner root sheath, one cell layer thick; first to develop trichohyalin granules and first to keratinize

89
Q

Why can’t the Henle’s layer and Huxley’s layer be distinguished in the isthmus?

A

both are fully cornified at this point

90
Q

What disease is induced by loss of the immune privilege of the hair follicle?

A

alopecia areata

91
Q

Histopathologic findings in proliferatve, lymphocytic, infundibular mural folliculitis with apoptosis and parakeratotic casts (PLIMF)

A

lymphocyte infundibular mural folliculitis (duh), hair follicle hyperplasia, parakeratosis, keratinocyte apoptosis with lymphocytic satellitosis

92
Q

What is kenogen?

A

empty follicle after exogen (hairless telogen)

93
Q

What time of year is cyclic flank alopecia most common?

A

hair loss usually occurs in winter or spring (shorter day-length)

94
Q

Histologic features of follicular lipidosis

A

lipid vacuoles within cells of hair follicle matrix

95
Q

T/F: Progesterone cross-reacts with the testosterone receptor.

A

True - causes negative feedback to the pituitary, inhibiting further gonadotropin secretion

96
Q

What breed of cow is over-represented with alopecia areata?

A

Eringer

97
Q

Histopathologic findings with feline degenerative mucinotic mural folliculitis

A

moderate to severe inflammation - inflammatory cells included lymphocytes, macrophages, plasma cells, neutrophils; spread from surrounding dermis to isthmus of hair follicle – often with extension to infundibulum

98
Q

What effect does estrogen have on the hair cycle?

A

inhibits hair growth – regulates the anagen-telogen hair follicle transition; decreases size of sebaceous glands and epidermal thickness (mice and rats); prolongs anagen in pregnant women; Shortens the anagen period, promotes catagen, lengthens the duration of telogen***; induction of of apoptosis by upregulation of signaling pathways (BMP4)

99
Q

What is the role of TGF-beta-1 in the hair cycle?

A

induces premature catagen

100
Q

What is congenital alopecia/hypotrichosis?

A

reduction in number of hair follicles formed OR hair follicles formed at normal density –> fail to regenerate following second or third catagen (additional ectodermal defects may exist)

101
Q

Simple hair follicles are seen in what species?

A

omnivores and herbivores: horses, cattle, pigs, rats, mice, etc. (NOT rabbits - they have compound hair follicles)

102
Q

Follicular lipidosis has been described in what breed(s)?

A

Rottweilers and a Dachshund dog

103
Q

Name the layers of the hair follicle from Outside to Inside

A

Connective tissue sheath (fibrous sheath) –> outer root sheath –> inner root sheath (Henle’s layer –> Huxley’s layer) –> cuticle –> hair shaft cortex –> hair shaft medulla

104
Q

Histopathologic findings with feline proliferative and necrotizing otitis and dermatitis?

A

marked epidermal and follicular hyperplasia with parakeratotic hyperkeratosis and lymphocytic, infundibular mural folliculitis and apoptosis

105
Q

T/F: The inner root sheath is not present in telogen.

A

True - and the entire inferior portion of the hair follicle has regressed

106
Q

Signalment of cats affected with feline degenerative mucinotic mural folliculitis

A

no breed predilection, males over-represented; median age of onset = 7 years

107
Q

T/F: In a telogen follicle, there is no inner root sheath cornification.

A

True - all trichilemmal cornification from the outer root sheath

108
Q

What treatment had the most success for proliferatve, lymphocytic, infundibular mural folliculitis with apoptosis and parakeratotic casts (PLIMF)?

A

cyclosporine

109
Q

What effect would activation of the sonic hedgehog signaling gene pathway have?

A

increase duration of anagen, increase size of hair follicle

110
Q

Which keratinizes first: Henle layer or Huxley layer?

A

Henle layer

111
Q

T/F: Humans have androgen-responsive follicles.

A

True - androgens are associated with increased hair growth (except eyelashes and scalp hair)

112
Q

Cells in the bulge area express high levels of what surface glycoprotein, that attenuates the inflammatory response

A

CD200

113
Q

Clinical signs of follicular dysplasia are apparent during what phase of the hair cycle?

A

anagen

114
Q

What is the role of the wingless (Wnt) signaling pathway in the hair cycle?

A

determines differentiation of epithelial stem cells into hair follicle keratinocytes

115
Q

Nonmedullated hair of sheep

A

Wool

116
Q

Diseases characterstic by isthmic mural folliculitis

A

pseudopelade, mucinotic mural folliculitis of lundehunds, degenerative mucinotic mural folliculitis, cutaneous and systemic lupus erythematosus (ECLE and GDLE primarily), granulomatous mural folliculitis

117
Q

Breeds predisposed to cyclic flank alopecia?

A

Airdale terriers, Boxer, English bulldog, French bulldog

118
Q

T/F: Feline degenerative mucinotic mural folliculitis responds well to glucocorticoids.

A

False - all cases published were euthanized after failure to respond to steroids

119
Q

Describe skin and hair of Xolo dogs with the Hm mutation

A

Thick epidermis with melanocytes and prominent rete pegs; comedones; many aborted hair follicle plugs –> cannot produce hairs –> most hair follicles undergo atrophy

120
Q

Histopathologic changes in cyclic flank alopecia

A

deformed telogen follicle (witch’s foot)

121
Q

What is the most important environmental influence on the hair cycle?

A

day length

122
Q

What are proposed effects of melatonin on the hair cycle?

A

may affect hair growth via increased concentrations of IGF-1 or GH; may induce anagen via estrogen receptor pathway; hair follicle itself can synthesize melatonin and the melatonin receptor is expressed in the hair follicle

123
Q

Which portion of the hair follicle is immune privileged: upper or lower? What changes are present in this site?

A

lower - lower number of APCs, suppressed MHC II antigen presentation, absence of MHC I in ORS and matrix cells; immunosuppressive mediators (alphaMSH, TGFbeta-1, ACTH); bulb devoid of lymphatics

124
Q

What effect does prolactin have on the hair cycle of sheep and minks?

A

stimulates shedding

125
Q

Exogenous factors that can lead to premature telogen induction

A

glucocorticoids, estrogen

126
Q

What are the components of the inner root sheath?

A

inner root sheath cuticle –> Huxley’s layer –> Henle’s layer –> companion layer

127
Q

Does BMP-4 (bone morphogenic protein) inhibit or stimulate hair growth?

A

inhibit

128
Q

What is the role of EGF in the hair cycle?

A

promotes catagen

129
Q

Congenital alopecia/hypotrichosis is described in what species? Mode of inheritance?

A

some forms are X-linked; described in dogs and cattle

130
Q

What effect does blocking the wingless (wnt) signaling pathway have?

A

prevents a new hair cycle

131
Q

Describe the bulbar region of the hair follicle

A

Highly proliferative matrix cells (transit amplifying cells or matrix progenitors) intermingled with melanocytes; matrix cells enclose the mesenchymal fibroblasts of the dermal papilla – separated from the matrix cells by a thin basement membrane

132
Q

T/F: Additional ectodermal defects may exist in combination with congenital alopecia/hypotrichosis.

A

TRUE - abnormal dentition, nails, lack of eccrine glands

133
Q

What effect does prolactin have on the hair cycle of Cashmere goats?

A

induces anagen

134
Q

Describe pathogenesis of acute telogen defluxion

A

Anagen is prematurely terminated –> all hairs are in telogen due to inciting factor –> telogen hairs shed in 2-3 months when follicles re-enter anagen

135
Q

What is the role of bone morphogenic protein signaling in the hair cycle?

A

maintains hair in telogen; prevents anagen initiation

136
Q

T/F: The medulla is not present in all hair shafts.

A

TRUE

137
Q

Describe the infundibulum of the hair follicle

A

orifice of the hair follicle to a small area at which trichilemmal cornification is seen (approximately the opening of the sebaceous gland duct into the HF); innermost epithelial cells of the infundibulum have keratohyalin granules

138
Q

What is the predominant inflammatory cell associated with mural mucinotic isthmus folliculitis of Lundehunds?

A

Cd3+ T cells

139
Q

What effect does trauma or wounding have on the hair cycle?

A

causes anagen induction – due to proinflammatory cytokines, decrease of BMP4, upregulation of wnt (wingless) and shh (sonic hedgehog) signaling; does not work during refractory telogen (no anagen induction); TNF-alpha: accelerates wound healing, stimulates hair regeneration through activation of wnt (wingless) signaling

140
Q

What effect does spaying have on FSH and LH concentrations?

A

increased FSH and LH, but LH receptors are decreased

141
Q

T/F: Puppies lose their puppy coast in the first 12-28 weeks of life.

A

False: they gain an adult coat – primary hairs develop secondary hairs

142
Q

What effect does estrogen have on human hair?

A

stimulates scalp hair growth – possible through anti-androgenic effects, or difference in estrogen receptors in human scalp hairs

143
Q

What is Adamson’s fringe?

A

Point at which cornification of the inner root sheath stops (i.e. both the Huxley layer and Henle layer are fully cornified)

144
Q

What signaling pathways are important in anagen initiation and promotion?

A

Sonic hedgehog (Shh) and Wingless (wnt) signaling

145
Q

Histopathologic changes in the skin of Sphynx cats with the Hr mutation

A

abnormal IRS; small curved hair follicles, primarily in anagen; produce hair shafts that are small and fragile; increased kenogen compared to normal; hair follicle density and follicle group size were not significantly different from normal**

146
Q

T/F: Melatonin can increase thyroid and adrenocortical activity.

A

False - has no effect on thyroid or adrenocortical activity

147
Q

T/F: Spontaneous remission is possible with both alopecia areata and mural mucinotic isthmus folliculitis of Lundehunds

A

False - reported with AA but not with MMIF of Lundehunds

148
Q

Signalment of dogs affected by alopecia areata?

A

GSD and Dachshund over-represented; no sex predilection; median agen of onset = 5 years

149
Q

What is the role of fibroblast growth factor 5 in the hair cycle?

A

terminates anagen

150
Q

T/F: Estrogen antagonists accelerate anagen once initiated by endogenous signals.

A

True - estrogen itself inhibits anagen, when it is removed, then the inhibition is removed

151
Q

Diseases characterstic by infundibular mural folliculitis

A

demodectic mural folliculitis, dermatophytic mural folliculitis, cutaneous and systemic lupus erythematosus, thymoma-associated exfoliative dermatitis, proliferative lymphocytic mural folliculitis with apoptosis, proliferative and necrotizing otitis externa in cats, granulomatous mural follicullitis

152
Q

Describe the changes that take place during early anagen (I-IIIb)

A

onset of growth, movement of dermal papilla into SQ, melanin production in bulb, DP becomes enclosed, hair shaft formation, hair reaches 2/3’s of follicle

153
Q

What effect does noggin have on BMP-4 (bone morphogenic protein)? What effect does this have on the hair cycle?

A

noggin is an antagonist of BMP-4 –> activity of noggin leads to hair growth as signaling by Shh, Wnt1 and STAT3 are no longer suppressed (BMP-4 suppresses these pathways)

154
Q

What is the role of insulin-like growth factor 1 in the hair cycle?

A

prevents the hair follicle from entering catagen; mediates growth promoting actions of GH on hair follicle growth

155
Q

Describe the pathogenesis of anagen defluxion

A

anagen phase is interrupted and hair falls out in 7-14 days without entering catagen or telogen => immediate anagen release, normal appearing anagen hair bulb; once trigger is removed, hair regrowth in 3-4 months; dystrophic form caused by chemotherapy, toxins, etc. in which the hair bulb is abnormal

156
Q

What anchors the hair shaft to the hair follicle in a catagen or telogen follicle?

A

trichilemmal keratin

157
Q

T/F: Alopecia X is more common in females than males.

A

False - occurs equally in female and male dogs regardless of neuter status

158
Q

What is the role of the vitamin D receptor in the hair cycle?

A

important for maintenance of keratinocyte stem cells in the bulge region; interacts with the wingless (wnt) signaling pathway; interacts with the sonic hedehog singaling pathway

159
Q

What is the etiology of feline proliferative and necrotizing otitis and dermatitis?

A

UNKNOWN!! (IHC negative for herpes, calicivirus, papillomavirus) – aberrant immune response suspected due to response to topical or systemic steroids or calcineurin inhibitors

160
Q

T/F: Color dilution alopecia is common in Weimaraners due to their dilute color.

A

FALSE

161
Q

Disease(s) characteristic by inferior/bulbar mural folliculitis

A

alopecia areata

162
Q

Portion of the hair follicle from the arrector pili muscle insertion to the entry of the sebaceous duct

A

Isthmus

163
Q

Age of onset of Mural mucinotic isthmus folliculitis of Lundehunds?

A

1.5 years

164
Q

In what part of the hair follicle are keratohyalin granules present?

A

infundibulum

165
Q

Which portion of the hair follicle has a high density of APCs: upper or lower?

A

upper – the lower portion is “immune privileged” and has low numbers of APCs

Vet Derm Review (44 decks)

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