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vet433b > Week 6 - Dermatology > Flashcards

Week 6 - Dermatology Flashcards

1
Q

What is Atopic Dermatitis?

A

-Allergic (inappropriate) reaction to
environmental antigens and other
triggers

-allergic response, mediated by IgE

-seasonal or year round

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2
Q

There is a genetic component to atopic dermatitis.

A

◦Multiple genes noted
◦Breed differences

strong genetic tendency in dogs, with golden retrievers, Labrador retrievers, terriers, Dalmatians, and Shar-peis

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3
Q

What CAUSES atopic dermatitis?

A

allergen gain access to body by
respiratory OR percutaneous route

  1. Hypersensitivity mediated by IgE antibodies
  2. Loss of Barrier function / barrier dysfunction
  3. Bacterial dysbiosis ?
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4
Q

How does HYPERSENSITIVITY cause atopic dermatitis?

A

Allergens interact with Langerhans’ cells, TH2 and B lymphocytes, cause allergen-specific IgE production

Allergens bind to allergen-specific IgE on
mast cells = degranulation & release of
inflammatory substances

Inflammatory cytokines released from keratinocytes and T-cells

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5
Q

Mast cells release what 2 things?

A

Histamine
Tryptase - most abundant mediator stored in
mast cell granules !!!!

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6
Q

How does LOSS OF BARRIER FUNCTION cause atopic dermatitis?

A

◦Abnormalities in lipid layer of the stratum corneum

◦Tight junction abnormalities

◦Decreased epidermal (functional) filaggrin
-Clinical importance not proven yet in dogs
-filaggrin: important component of the stratum corneum (the outer most, ‘horny’ layer of the epidermis - may translate into more susceptibility to both allergen and infective organism access to the skin
-not seen in westies (WHWT)

Allows:
◦allergen ‘penetration’ via stratum corneum
◦Staphylococcus spp (& Malassezia) to ‘stick’ to the stratum corneum
◦Water loss

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7
Q

What is the DOG SIGNALMENT for Atopic Dermatitis?

A

Age at onset: 1-7 years; mean at UC Davis: 1.66 yrs

Breed: Retrievers, Terriers, Dalmatians, Shar-peis, Shiba inus, French bulldogs

No sex predilection

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8
Q

What are the DOG CS for Atopic Dermatitis?

A

Pruritus
Erythema
Rarely, small papules
Feet, face, axilla, ears, conjunctivitis

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9
Q

What is CAT SIGNALMENT for Atopic Dermatitis?

A

Etiology: presumed to be similar to
dogs

No age or sex predilection

Himalayans, Persians, Abyssinians at greater risk

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10
Q

What are the CAT CS for Atopic Dermatitis?

A

Facial / head / neck pruritus
Miliary dermatitis
Eosinophilic granuloma complex
Self-induced alopecia

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11
Q

How do you DIAGNOSE Atopic Dermatitis?

A

history
physical examination
and (except in the “classic” case of recurrent, strictly seasonal “typical” clinical signs, erythema/pruritus of face, etc.) ruling out other causes of pruritus, especially food allergy, ectoparasites, etc

History
◦seasonal, < 7 years old at onset
Clinical Signs
◦pruritus feet, face, axilla, ears
Rule outs
◦food allergy, ectoparasites, etc

-Classic: seasonal, typical lesion distribution
-Semi-classic: non-seasonal or non-typical lesion distribution
-Not classic: rule outs fail

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12
Q

What Secondary Infections can mainly dogs, some cats, get from atopic dermatitis?

A

Staphylococcus pseudintermedius
Malassezia pachydermatis

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13
Q

If owners are interested in HYPOSENSITIZATION from atopic dermatitis, what testing would you do?

A

looking for allergen-specific IgE –>

  1. Intradermal testing (IDT)
  2. Serologic testing
    ◦ELISA
    ◦VARL-EIA
    ◦RAST

because of high incidence of “false positive” (or, at least, clinically non-relevant) findings, these
tests should only be performed if other diagnoses have been ruled out.

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14
Q

What is hyposensitization?

A

-therapy to try and get rid of allergies

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15
Q

What % of dogs improve with hyposensitization?

A

70% of dogs that improve, do so within 4-6 months

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16
Q

How long should hyposensitization last?

A

Hyposensitization should be continued for at least 1 year before final evaluation of
efficacy.

If effective, the treatment will almost certainly need to be continued for the animal’s life.

17
Q

How do you TREAT Atopic Dermatitis?

A

Systemic
◦Corticosteroids, antihistamines, EFAs,
cyclosporine, oclacitinib, lokivetmab,
maropitant (cats)

Topicals
◦Steroids, barrier aids

18
Q

What CORTICOSTEROIDS do you use for DOGS and CATS with Atopic Dermatitis?

A

Dogs:
◦Prednisone, prednisolone,
methylprednisolone
◦ 1 mg/kg/d, then taper

Cats:
◦Prednisolone, methylprednisolone:
1.5 mg/kg q24h, then taper
◦Triamcinolone:
0.8 mg/kg q24h, then taper

19
Q

What ANTIHISTAMINES do you use for DOGS and CATS with Atopic Dermatitis?

A

Dogs:
-Cetirizine 1mg/kg bid
–cetirizine is the active metabolite of hydroxyzine, so if one doesn’t work, the
other probably won’t either
–does not work in cats
-Diphenhydramine 2.2 mg/kg tid
-Hydroxyzine pamoate 2.2 mg/kg tid
-Chlorpheniramine 0.2-0.8 mg/kg bid-tid
*antihistamines not orally bioavailable or need large doses

Cats:
-Chlorpheniramine 2-4 mg/5 kg bid
-Clemastine 0.1 mg/kg bid

20
Q

Which drug is helpful in reducing the amount of prednisone which must be given to atopic dogs?

A

trimeprazine 5mg and prednisolone 2 mg

(Temeril-P® [Vanectyl-P® in Canada], Zoetis)

21
Q

What ESSENTIAL FATTY ACIDS do you use for DOGS and CATS with Atopic Dermatitis?

A

-nonsteroidal antipruritics

Dogs:
-Omega 3: fish oil, flax
◦Eicosapentaenoic Acid (EPA)
◦Docosahexaenoic Acid (DHA)
-Omega 6: EPO, borage
–25%- 40% AD dogs improve
–May take >3 months
–Steroid-sparing

◦Omega 3 dose: 66 mg per kg body
weight of combined
-No need to use omega 6!
-6-12 weeks for full effect

-These drugs interfere with the production and metabolization of arachidonic acid and other “pro-inflammatory” substances

Cats:
-Antihistamines + essential fatty acids may give relief from clinical signs in as high as 50% of atopic cats

22
Q

How does Cyclosporine help treat Atopic Dermatitis?

A

-calcineurin inhibitor, mode of action: inhibit
T cell activation

-Atopica®, Elanco; CyclavanceTM , Virbac

SIDE EFFECTS:
Anorexia, vomiting, diarrhea
Papillomas, pyoderma
Hypertrichosis
Renal / hepatic disease (rare)
Gingival enlargement

to minimized vomiting:
-Keep in freezer and give frozen
-Give with food
-Give with maropitant citrate (Cerenia
®, Zoetis) for 3-5 days

-Ok to test (skin or serologic) for
allergies while receiving
-Ok to hyposensitize while receiving

Cats:
liquid preparation of Atopica have a similar
effective decrease in their pruritus

-Cats infected with T. gondii prior to CsA administration failed to develop clinical illness after administration of CsA

-Cats that have high CsA concentrations
when first exposed to T. gondii can develop
fatal infection
–Ideally test cats for both IgG and IgM
serology
–Keep treated cats indoors

23
Q

What is Apoquel and how does it treat Atopic Dermatitis?

A

-only for dogs

-oclacitinib – Zoetis

-Janus-kinase-1 inhibitor interferes with interleukin effects especially IL 31 (mediator of pruritus at the nerve level)

-well-tolerated by dogs and suppresses
pruritus rapidly (within 24 hours)

-contraindications: a history of demodicosis or neoplasia

-Ok to test (skin or serologic) for allergies; ok
to hyposensitize concurrently

-Side effects: gastrointestinal upset and lethargy have been noted, and rare elevations of liver enzymes may occur. Rare cases of generalized demodicosis have been noted

24
Q

What is Cytopoint and how does it treat Atopic Dermatitis?

A

-only for dogs

-Lokivetmab

-Caninized mouse antibody targeting interleukin 31

-monthly injection
-Good safety profile
-Somewhat expensive in large breed dogs
-Not to be used for cats (ineffective)

25
Q

How do Apoquela nd Cytopoint differ in targeting?

A

Apoquel - targets Janus-kinase-1 (which ultimately effects interleukin 31

Cytopoint - antibody that targets interleukin 31

26
Q

There are TOPICAL CORTICOSTEROIDS that can be used to treat Atopic Dermatitis

A

◦GenesisTM Spray: Virbac (0.015%
triamcinolone acetonide)

◦Triz-ChlorTM 4 HC: Dechra (1 %
hydrocortisone)

◦CortavanceTM Spray: Virbac (0.0584%
hydrocortisone aceponate)
-metabolized in the dermis. This spray has a low risk of corticosteroid side-effects if used
on problem areas (especially the feet) to ‘cool down’ the pruritic response
-not in US

27
Q

There are TOPICAL NON-STEROIDALs that can be used to treat Atopic Dermatitis

A

-Dermoscent
–topical spot-on with omega-3 and -6 fatty acids which claims to be effective in restoring the barrier function of the epidermis in atopic dogs.

28
Q

What is Malasezzia? (in dogs)

How does it present?

A

Yeast organism, normal inhabitant of skin

◦Waxy brown exudate: skin or proximal claws,
erythema interdigitally or under tail
◦Interdigital, folds, generalized
◦Other species reported
◦Usually secondary to atopic dermatitis and/or
food allergy

29
Q

What species of Malasezzia are there present in dogs?

A

M pachydermatis was the greater population in
atopic dogs, vs M restricta in healthy dogs

also in cats:
M globosa, M restricta, M furfur, M
pachydermatis, M nana and M sympodialis

30
Q

Where has Malasezzia been isolated in cats?

A

isolated from the skin and ear canals of healthy cats as well as from cats with dermatitis and otitis

31
Q

What is Malasezzia associated with in cats?

A

Malasseiza dermatitis may be associated with
-atopic dermatitis
-food allergy
-internal neoplasia (thymoma, adenocarcinoma of the pancreas) cutaneous lymphoma
-pemphigus foliaceus.

32
Q

How do you DIAGNOSE Malasezzia Pachydermatis?

A

-cytology via acetate (‘ScotchTM’) tape
preparation or skin scrapings

-Clear Tape Preparations Procedure:
◦Press on lesion(s)
◦Place on slide (sticky side down)
◦Stain for bacteria & yeast (100x) w Dif-Qwik

33
Q

How do you TREAT Malasezzia Pachydermatitis?

A

Anti-Yeast Rx: SYSTEMIC
-Terbinafine 30 mg/kg q 24h
–reduced cost
-Fluconazole, Itraconazole
-Ketoconazole
◦Not in cats; not w/ ivermectin 5 mg/kg q 24h
**Treat for at least 1 month

Anti-Yeast Rx: TOPICAL - for restricted areas
-Miconazole
-ketoconazole
-Chlorhexidine
-Acetic acid 2.5% & boric acid 2%
**2x per week

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