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Small Animal Medicine II > Atopic Dermatitis > Flashcards

Atopic Dermatitis Flashcards

1
Q

What are 3 parts to the pathogenesis of atopic dermatitis?

A
  1. damage/dysfunction of epidermal barrier allows increased exposure to allergens and secondary infections
  2. genetic predisposition to Type I hypersensitivities (allergen access body via skin)
  3. aberrant immune response - shift in cytokines that regulate immune responses to increased Th2 cells over Th1 and lymphocytes
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2
Q

What cytokines and cells are increased in dogs with atopic dermatitis?

A
  • IL-31
  • IL-17
  • Treg cells
  • IL-4 (in skin)
  • IL-34
  • Th2 cells
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3
Q

Why are secondary infections commonly seen with atopic dermatitis?

A

damage to the epidermal barrier allows increased adherence of bacteria and yeast, resulting in increased carriage of bacteria (S. pseudintermedius)

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4
Q

In what 3 conditions is atopy considered the primary factor?

A
  1. pyoderma - all forms, acral lick dermatitis, other regional pyoderma
  2. Malassezia dermatitis
  3. otitis externa
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5
Q

What does relevance of allergens depend on? What are the 4 major categories?

A

volume, buoyancy, allergenicity, geographic distribution

  1. pollens - grass, trees, weeds
  2. molds
  3. epidermal - human, horse, cat
  4. misc - house dust mite, feathers, wool, tobacco, kapok (tree pod), cotton liners, insects (chitin)
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6
Q

What is the top allergen of humans and dogs?

A

house dust mite

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7
Q

How can seasons be used to differentiate possible causes of atopy?

A
  • SPRING - tree pollen, molds
  • SUMMER - grass pollen, weed pollen, mold
  • FALL - weed pollen, mold
  • WINTER - indoor allergens, mold
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8
Q

What are the major clinical causes of itch?

A
  • parasites - mange
  • infectious - pyoderma
  • allergy
  • inflammation

use database for rule out other causes –> left with atopic dermatitis if they are negative

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9
Q

When do clinical signs of atopic dermatitis typically occur? What are 2 key clinical features?

A

1-3 y/o

  1. pruritus PRECEDES lesion - mild to moderate, responds to glucocorticoids if secondary infection is not present
  2. seasonality progresses to year-round signs
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10
Q

What differentials are associated with severe/mild itch?

A

SEVERE - sarcoptic mange, flea allergy, Malasseazia, seborrhea

MILD - allergies

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11
Q

What factors typically lower the itch threshold?

A

increases itch

  • breed
  • heat
  • dry skin
  • inflammation
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12
Q

What factors typically increase the itch threshold?

A

decrease itch

  • breed
  • cool temperature
  • hydrated skin
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13
Q

What 3 physical exam findings are commonly associated with atopic dermatitis?

A
  1. erythema, excoriation, and scale in thin-skinned areas
  2. chronic - hyperpigmentation, lichenification
  3. secondary infection - S. pseudintermedius, M. pachydermatis
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14
Q

What breeds have a predilection for developing atopic dermatits?

A
  • Terriers
  • Golden Retriever
  • Lab
  • English Bulldog
  • French Bulldog
  • Chinese Shar-Pei
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15
Q

What is the hallmark of atopic dermatitis?

A

pruritus preceding lesion development

  • licking
  • rubbing
  • scratching
  • chewing
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16
Q

What distribution of lesions are characteristic of atopic dermatitis? What are 3 concurrent clinical features seen?

A

thin-skinned areas –> peri-ocular, interdigital, axilla, ventral abdomen (depends on breed!)

  1. perianal pruritus - can lead to recurrent anal sac inflation and infection
  2. recurring otitis externa
  3. recurring pyoderma - superficial, acral lick dermatitis
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17
Q

Atopic dermatitis:

A

characteristic abdomen, periocular skin, interdigital areas, perianal

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18
Q

Atopic dermatitis:

A

dorsal AND ventral interdigital skin

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19
Q

Atopic dermatitis:

A

traumatic conjunctivitis due to rubbing face on ground to itch periorbital skin

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20
Q

What is the main manifestation of atopic dermatitis in cats? What 2 other clinical features are commonly seen?

A

licking of ventral abdomen and extremities

  1. feline reaction patterns - eosinophilic granuloma complex –> eosinophilc plaques, collagenolytic granuloma, indolen ulcers + military, chin, and exfoliative (scale) dermatitis
  2. otitis externa
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21
Q

Atopic dermatitis, cat:

A

patchy, thin skin due to licking

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22
Q

Atopic dermatitis, cat:

A

reaction pattern - miliary dermatitis

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23
Q

How is atopic dermatitis diagnosed?

A
  • signalment, history, PE, response to treatment
  • dermatologic database
  • allergy testing - intradermal, in-vitro allergy tests
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24
Q

What are 7 clinical criteria indicative of atopic dermatitis? What 2 criteria can rule it out?

A
  1. onset <3 y/o
  2. dog living mostly indoors
  3. glucocorticoid responsive
  4. pruritus without lesions at onset
  5. affected front feet and ear pinnae
  6. non-affected ear margins (sarcoptic mange)
  7. non-affected dorsolumbar area (flea allergy dermatitis)
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25
Q

What is the purpose of performing intradermal skin testing? What are the 4 keys to success?

A

confirm diagnosis and provide information about hyposensitization

  1. patient selection
  2. patient preparation
  3. quality of antigens
  4. technique and interpretation
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26
Q

What occurs if an intradermal injection for allergy testing is done too deep?

A

goes into superficial dermis, where mast cells are –> no reaction seen even if allergic

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27
Q

What confirms intradermal location for skin allergy testing? When should reactions be read?

A

wheal development –> wheal + flare = +

in about 10 mins

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28
Q

What positive and negative controls are used for skin allergy testing?

A

POSITIVE = histamine

NEGATIVE = saline

29
Q

What can help when assessing intradermal skin allergy tests?

A

indirect light = easier to see wheal and inflammation

30
Q

What are in-vitro allergy tests? What are 3 advantages? Disadvantage?

A

detection of circulating antigen-specific IgE

  1. minimal drug withdrawal
  2. rapid, easy - blood collection
  3. no special supplies needed

higher tendency to give false positive results - increased background IgE (parasitism)

31
Q

Intradermal vs. serologic allergy testing:

A
32
Q

How is allergy testing interpreted?

A
  • fitting the clinical picture - seasonality, geographical area, severity of pruritus
  • determining therapy - if unclear, consider symptomatic treatment first
33
Q

What are 3 parts to managing atopic dermatitis?

A
  1. support epidermal barrier
  2. control infections - Malassezia pachydermatis, S. pseudintermedius
  3. decrease itch
34
Q

What ingredients in topicals are best for supporting epidermal barriers?

A

lipids - ceramides, fatty acids, essential oils, ophytrium

  • omega 6 > omega 3
35
Q

When is maintenance therapy began for cases of atopic dermatitis? What is done? How long?

A

after infections are cleared

  • weekly baths
  • wipes, mousses, or sprays on predisposed areas

FOREVER or until underlying allergy is fully controlled

36
Q

What are 4 options for controlling pruritus in cases of atopic dermatitis? What is commonly added?

A
  1. glucocorticoides
  2. cyclosporine
  3. IL-31 blockers - Oclacitinib, Lokivetmab
  4. allergen-specific immunotherapy (hyposensitization)

steroid-sparing agents - antihistamines, fatty acids, topicals

37
Q

When are topical therapies for itch associated with atopic dermatitis especially useful? What are 3 shampoo options?

A

withdrawal period of glucocorticoids prior to allergy testing

  1. colloidal oatmeal - keratinolytic, hydrates skin, 24 hours
  2. pramoxine - topical anesthetic, 2 days
  3. glucocorticoids - hydrocortisone only, much longer, $$$
38
Q

How are wipes used for controlling itch associated with atopic dermatitis?

A

clean feet and other problem areas once daily to remove allergens from the skin

39
Q

What supportive therapy is recommended when treating pruritus associated with atopic dermatitis? What 2 functions do they have?

A

fatty acids and antihistamines –> ineffective by themselves, synergistic together, highly recommended for dogs on steroids

  1. reduce anxiety
  2. support skin barrier
40
Q

What 3 glucocorticoids are used to treat pruritus associated with atopic dermatitis?

A
  1. prednisolone - cat
  2. prednisone - dog
  3. methylprednisolone

good potency long-term

41
Q

What is the protocol for Prednisone/Prednisolone treatment for atopy?

A
  • 1.1 mg/kg SID, PO for 5-7 days
  • 1.1 mg/kg EOD, PO for 14-21 days
  • slowly decrease dose by 10-20% every 10-21 days (5-10 doses)
  • end maintenance dose of 0.5-1.1 mg/kg EOD

(if there is no itch control, secondary infection is still likely there)

42
Q

What are some advantages and disadvantages to glucocorticoid therapy for pruritus in cases of atopy?

A

ADVANTAGES - highly effective, inexpensive, easy to dose

DISADVANTAGES - Cushing’s like adverse effects (PU/PD, nocturia, polyphagia, panting, personality changes), easy to mess up dosing

43
Q

When are higher doses commonly needed for glucocorticoid therapy? What should owners be warned about?

A

severe allergy seasons

avoid daily dosage after initial induction period –> affects HPA axis daily, EOD still necessary but dose can be increased

44
Q

What is another glucocorticoid that may be effective for cases of atopy?

A

Temaril-P –> 2 mg prednisolone + 5 mg trimeprazine tartrate

  • appears to allow lower doses, but same side effects are associated and $$$
45
Q

What forms of glucocorticoids are contraindicated for atopy treatment?

A

injectables –> HPA axis!

46
Q

Glucocorticoids, adverse effects:

A

Cushingoid - calcinosis cutis, alopecia

47
Q

What are 2 options for topical glucocorticoids? How often are they given? How are they best used?

A
  1. Triamcinolone
  2. Betamethasone - readily absorbed, hair loss common (strong!)

BID for a week –> SID for a week –> twice weekly

spot treatment or occasional adjunct (will affect HPA axis!)

48
Q

What 3 situations may result in prednisolone-resistant pruritus?

A
  1. true resistance - possible, but not confirmed
  2. non-prednisone responsive disease - food allergy
  3. secondary infection - Staph, Malassezia
49
Q

When is Cyclosporine recommended for treating atopy? How long/often? What can reduce dose?

A

control pruritus

plan for SID dosage for 3-6 weeks –> full effect often takes 6 weeks, then reduce

add Ketoconazole

50
Q

What 5 adverse effects are associated with Cyclosporine therapy?

A
  1. vomiting
  2. glucose metabolism disturbance
  3. papillomatosis, cutaneous neoplasm - immunosuppression
  4. gingival hyperplasia
  5. infections - UTI, opportunistic

+ expensive, compounded not recommended

51
Q

What IL-31 blockers are available for cases of pruritus seen in atopy?

A

APOQUEL (oclacitinib) - oral, blocks JAKSTAT receptors

CYTOPOINT (IL-31 monoclonal antibody) - canine IgG against IL-31, SQ

52
Q

How does Apoquel (oclacitinib) work? In what dogs is it contraindicated?

A

JAK inhibitor selective for JAK1 pathway, which downregulates IL-2, 4, 6, 13, and 31

dogs <12 months of age –> immune dysfunction can cause demodicosis

53
Q

What are 3 advantages to using Apoquel in cases of atopy? 2 disadvantages?

A

ADVANTAGES - highly effective, works fast, few adverse effects at label doses short-term

DISADVANTAGES - not as selective, no residual activity into the night when given in the morning (try for noon SID)

54
Q

What adverse effects have been reported with Apoquel?

A
  • GI upset
  • demodicosis (<1 y/o)
  • hematologic abnormalities
  • increased cutaneous masses
  • seizures
  • weight gain

more common in high doses and chronic administration

55
Q

What are the 2 main indications for Apoquel?

A
  1. rapid response to pruritus when CS is not an option
  2. induction period of immunotherapy (up to 9 months)

price point is variable depending on size

56
Q

How long is Cytopoint typically effective for? How does it compare to Apoquel?

A

4-6 weeks

  • more consistent
  • reduces client compliance
  • price point variable
57
Q

How does immunotherapy work? What 4 things does this result in?

A

gradual exposure to increasing doses of allergen and reduces mast cell and basophil triggering

  1. increases Treg cells, which represses immune response and produces IL-10 and TGF-b to reduce B cell production of IgE and inhibit inflammation
  2. increases Th1 over Th2
  3. higher IFN-y/IL-4 ratio
  4. forms IgG as a blocking antibody
58
Q

Why consider immunotherapy?

A
59
Q

What are the 4 major advantages to immunotherapy?

A
  1. several options available - traditional, rush, regional-specific, sublingual
  2. alters immunologic pathways - possible cure
  3. more effective when primary manifestation of allergy is infection
  4. overall pretty successful (35-70%)
60
Q

What are 5 disadvantages to immunotherapy?

A
  1. price point is variable - great cost/benefit ratio for larger dogs
  2. injectable options require training
  3. sublingual options difficult
  4. adverse effects - increased itch, urticaria, anaphylaxis
  5. requires knowledge of allergens - testing is important
61
Q

What is the normal immunotherapy protocol?

A
  • weekly injections until maximum efficacy (4-9 months)
  • reduce to every 10-14 days
  • continue reduction every 2-4 months

seasonal variation - more frequent injections during allergy season

62
Q

What are 2 major problems with commercial allergy testing and hyposensitization?

A
  1. allergens selected are based on numbers, which can be misleading with no consideration of geography, pet, or environment
  2. standard schedule and reduction of frequency of injections, not based on patient response
63
Q

How does sublingual immunotherapy work? How often is it given?

A

absorption by lymphoid tissues located in the oral cavity

BID, under the tongue

64
Q

What are some options of combination therapy used for atopy?

A
  • glucocorticoids and antihistamines
  • antihistamines and EFAs
  • glucocorticoids and EFAs
  • Apoquel/Cytopoint and antihistamines/glucocorticoids
  • topicals
  • immunotherapy

combo therapy is always superior to a single-drug treatment

65
Q

In what patients do glucocorticoids work best? Less likely?

A
  • need of rapid response
  • need anti-inflammatory effects
  • seasonal, short-term
  • cost

concurrent health issues, patient can not tolerate, plan to allergy test

66
Q

In what patients do cyclosporine work best? Less likely?

A
  • small dogs and cats
  • some anti-inflammatory effect desired (GC not an option)

concurrent infections, DM, cost is a factor

67
Q

In what patients do Apoquel work best? Less likely?

A
  • need rapid response
  • prior to allergy testing
  • while waiting for immunotherapy
  • cost

long-term use, does not provide 24 hrs of relief

68
Q

In what patients do Cytopoint work best? Less likely?

A
  • client compliance
  • convenience
  • adverse effects to other options

clients are not mobile, large dogs (cost)

69
Q

In what patients do immunotherapy work best? Less likely?

A
  • younger dogs
  • infections, otitis main manifestations
  • owners prefer to treat disease vs masking symptoms

client compliance/ability to administer treatment, owners want short-term gratification

Small Animal Medicine II (57 decks)

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