Atopic Dermatitis (Marsella) Flashcards

1
Q

Atopic dermatitis (AD)

A
  • Inherited
  • Relapsing
  • Pruritic dermatitis
  • Commonly associated w/ IgE against environmental allergens
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2
Q

Possible AD pathogenesis (general)

A
  • Type I hypersensivity (IgE, allergy)
  • T cell imbalances
  • 1º skin barrier defect
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3
Q

AD pathogenesis via inhalantion of allergens

A

Allergen is inhaled & systematically absorbed → IgE migrates to tissue & binds to mast cells

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4
Q

AD pathogenisis via percutaneous absorption

A

Allergen is captures by Langerhans cells in the skin → local produciton of IgE

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5
Q

Clinical signs of AD in dogs

A
  • Familial hx
  • Breed predilection (terriers, shar peis, setters, retrievers, beagles, dalmatians, cockers)
  • Onset 1-3 yrs old
  • Season signs at 1st
    • Progressive worsenig w/ time
  • Pruritis & erythema (face, feet, ears, groin, axillae)
    • Front feet 1st, then progresses to all
  • Chronic: excoriations, lichenification, hyperpigmentation
  • 2º ear & skin infections (pyoderma, malassezia)
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6
Q

AD in cats

A
  • Young adults
  • Progressive
  • Pruritis
  • Symmetrical alopecia
  • Miliary dermatitis
  • Eosinophilic granuloma complex
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7
Q

AD diagnosis

A
  • History
  • Clinical signs
  • Exclusion of other pruritic dz
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8
Q

Willemse’s MAJOR criteria for diagnosis of AD

A

At least 3 major and 3 minor criteria

  • Major
    • Pruritis
    • Facial and/or digital involvement
    • Lichenification of flexor surfaces
    • Chronicaly relapsing dermatitis
    • Familial hx
    • Breed predilection
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9
Q

Willemse’ MINOR criterial for diagnosis of AD

A

At least 3 major and 3 minor criteria

  • Minor
    • Onset of clinical signs before 3 yrs old
    • Facial erythema
    • Bacterial conjunctivitis
    • Superficial pyoderma
    • Hyperhydrosis
    • Positive skin test
    • Elevated allergen specific IgE
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10
Q

Why do we do allergy testing?

A

To select allergens to use for immunotherapy

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11
Q

Intradermal skin testing (IDST) - general info

A
  • Evaluate presence of IgE in the skin
  • Small amounts of allergen are injected in the skin
  • Evaluate mast cell degranulation
  • Treat all concurrent diesases before testing
  • Off steroids & antihistamines for 2 mos
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12
Q

Intradermal skin test (IDST) process

A
  1. Sedate (xylazine)
  2. Inject
    • Negative control (saline)
    • Positive control (histamine)
    • Allergens
  3. Wait 15 minutes
  4. Evaluate
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13
Q

Intradermal skin test (IDST) evaluation

A
  • Subjective - visualization
    • Erythema
    • Induration
    • Size
  • Objective
    • measurement of wheal (hive)
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14
Q

False positive on IDST

A
  • Irritant allergens
  • Contaminated allergens
  • Skin sensitizing antibodies
  • Poor technique
  • Substances that trigger mast cell degranulation
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15
Q

False negative on IDST

A
  • Subcutaneous injection
  • Too little allergen
  • Outdated allergen
  • Steroids
  • Antihistamines
  • Tranquilizers
  • Progestational compound
  • Anergy (peak of the season)
  • Off season testing
  • Estrus, pseudopregnancy
  • Severe stress
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16
Q

In vitro allergy testing - Serology

A
  • Measurement of circulated allergen specific IgE
    • Radioallergosorbent test (RAST)
    • ELISA
  • Usually poor correlation w/ IDST
17
Q

Advantages of serology

A
  • No need to clip
  • No need to discontnue drugs (steroids & antihistamines)
  • No need to keep in stock allergens
18
Q

Disadvantages of serology

A
  • Poor correlation w/ IDST
  • False positives (non specific binding)
  • Not reproducible results
19
Q

AD therapy

A
  • Treat concurrent dz
    • other allergies
    • skin infections
  • Allergen avoidance
  • Hyposensitization (allergy vax)
  • Systemic therapy
  • Topical therapy
20
Q

Hyposensitization

A
  • 60-80% efficacy
  • Good option if prolonged season of pruritis
  • No results for first 3 mos
  • Life long therapy
  • Based on positive rxns
  • No more than 12 allergens/vax
21
Q

Adverse effects of hyposensitization

A
  • Rare
  • Incr. pruritis
  • Anaphylaxis
  • Urtiaria
22
Q

Systemic therapy - Glucocorticoids

A
  • Low dose, oral
  • Decr. efficacy over time
  • Long term side effects
  • Palliative
  • Indicated only w/
    • short season
    • no concurrent pyoderma
    • no concurrent demodicosis
23
Q

Systemic therapy - Cyclosporins

A
  • Immunomodulant (suppresses T cells & cytokine production)
  • Life long therapy
  • Monitor for infections
  • Adverse effects
    • drug interactions, GI, papillomatous dermatitis
24
Q

Oclacitinip (Apoquel)

A
  • Targets pruritis of various causes
  • JAK inhibitor
  • Extremely effective & fast acting
  • May precipitate demodicosis
25
Q

IL-31 monoclonal antibody

A
  • Inject once a month
  • Blocks IL-31 (important in transmission of pruritis)
  • Not as effective as other therapies
  • Considered adjunctive
26
Q

Antihistamines

A
  • Effective 40-50%
  • Better for prevention rather than tx of pruritis
  • Side effects
27
Q

Essential fatty acids

A
  • Anti-inflammatory (modulate leukotrienes)
  • Improve barrier function
  • Restoration of normal lipid composition
28
Q

Topical therapy

A
  • Frequent, cold baths
  • Oatmeal
  • Topical anesthetic (pramoxine)
  • Topical anthistamine
  • Lime sulfur
  • Topical steroids
  • Capsaicin
  • Topical calcineurin inhibitors
29
Q

Topical steroids

A
  • Triamcinolone spray
  • Leave on hydrocortisone
30
Q

Capsaicin

A
  • Active ingredient of chili pepper
  • Used for localized pruritis (lick granuloma)
  • Initial worsening
  • Prolonged relief
31
Q

Tacrolimus

A
  • Topical calcineurin inhibitor
  • Minimally absorbed (safe)
  • Effective esp. for localized cases
  • Initial burning sensation
32
Q

Treatments to restore barrier function

A
  • Phytosphingosine
  • Ceramides
  • Essential fatty acids
  • Emollients