Lecture: Atopic Dermatitis Flashcards
(46 cards)
1
Q
Atopic dermatitis
def
A
- genetically inherited
- relapsing
- pruritic dermatitis
- most commonly assoc with IgE against environeomntal allergens
2
Q
Atopic D.
Pathogenesis
A
- Clinical syndrome with different mechanisms in different patients
- Type I hypersensitivity IgE
- controversies
- affected dogs with normal IgE
- Normal dogs with high allergen specific IgE
- T cell imbalances
- Primary skin barrier defect
- controversies
3
Q
cyclosporin focuses on
A
T cells
4
Q
Mast cell degranulation
A
- pre-formed mediators
- Proteases
- Heparin
- Histamine
- Newly-formed mediators
- Prostaglandins
- Leukotrienes
- Cytokins (IL-1, IL-6, TNF-a)
5
Q
AD acute disease
A
- IL-4; IL-5 => T helper 2
- Increased IgE production
*These are susceptible to antihistamines
6
Q
AD Chronic disease
A
- IL-2; g-IFN => T helper 1
* these cytokines suppressed by cyclosporin
7
Q
AD as disease of skin barrier
A
- Abnormalities in upper layers ofepidermis
- increased skin permeability and allergen penetration
- higher risk for allergic sensitization
*ceramides fill in holes in skin barrier
*filagrin replaces missing protein….
8
Q
AD Pathogenesis
Route of allergen access
A
- Inhalation
- Percutaneous absorption (most important route in dogs)
- does no good to draw blood
- better to do a skin test for cutaneous IgE
9
Q
Clinical signs of AD in dogs
A
- familial history
- strong breed redilection
- Terriers
- Shar-Pei
- Setters
- Retrievers
- Beagles
- Dalmations
- Cockers
- Onset between 1-3 years of age (younger in FL)
- Seasonal at first
- Pruritus and erythema
10
Q
Areas of Pruritus and erythema in AD dogs
A
- Face
- Feet
- Ears
- Groin
- Axillae
11
Q
Rusty colored nail beds
A
- yeast infection in nail beds
12
Q
Chronic signs of AD
A
- chronicity
- excoriations
- lichenification
- hyperpigmentation
- Secondary ear and skin infections
- Pyoderma
- Malassezia dermatitis and otitis
13
Q
Atopic Dermatitis in cats
A
- young adults
- progressive worsening with age
- Clinical signs
- pruritus
- symmetrical alopecia
- miliary dermatitis
- Eosinophilic granuloma complex
*This cat often flea allergic as well
14
Q
Diagnosis of AD
A
- CLinical
- history
- clinical signs
-
exclusion of other pruritic dz
- scabies
- food allergy
- flea allergy
15
Q
Willemse’s criteria for dx AD
three of the major criteria
A
- pruritus
- facial and/or digital involvement
- lichenificati of flexor surfaces
- chronically relapsing dermatitis
- familial history
- breed predilection
16
Q
Willemse’s criteria for dx AD
minor criteria
A
- positive skin test
- elevated allergen specific IgE
17
Q
Allergy testing
A
- Why
- to select allergens to use for immunotherapy
- two types of testing
- IDST
- Serology => lots of false positive
18
Q
Intradermal skin testing
A
- Evaluate presence of IgE in the skin
- Small amounts of allergens are injected into skin
- evaluation of mast cell degranulation
19
Q
Intradermal skin test
Procedure/to know
A
- Before skin testing
- treat all concurrent diseases
- off steroids for 2 months
- off antihistamines for 2 weeks
- select allergens of the area
- clip area on lateral thorax
- sedate patient (xylazine)
- inject 0.05 cc ID
- negative control (saline)
- positive control (histamine)
- allergens
20
Q
Evaluation of skin test
A
- Immediate reactions
- 15 minutes
- Subjective
- Erythema
- Induration
- Size
- Objective
- measurement of the wheal
21
Q
False positive reactions
A
- Irritant allergens
- comtaminated allergens
- skin sensitizing antibodies
- poor technique
- substances that trigger mast cell degranulation
22
Q
False negative reactions
A
- Subcu injections
- too little allergen
- outdated allergen
- steroids
- antihistamines
- tranquilizers
- progestational compound
- anergy (peak of season)
- off season testing
- estrus, pseudopregnancy, severe stress
23
Q
Disadvantages of serology
A
- poor correlation wth IDST
- False positive (non-specific binding)
- Not reproducible results
24
Q
Therapy
A
- Treat any concurrent disease
- other allergies
- skin infections
- Allergen avoidance
- Hyposensitization (allergy vaccine)
- Systemic therapy
- Topical therapy
25
Hyposensitization
* effective in 60-80 % of cases
* good option if prolonged season of pruritus
* no results for first 3 months
* life long therapy
26
Hyposensitization
more
* Based on positive reactions
* no more than 12 allergens/vaccine
* adverse effects
* rare
* increased pruritus
* anaphylaxis
* urticaria
27
Anaphylaxis in dogs
GI upset
Vomiting, diarrhea, collapse
28
glucocorticoids
* palliative therapy
* oral steroids
* pulse therapy (low dose on alternate days)
* decreased efficacy over time
29
Indications for glucocorticoids
* short season
* No concurrent pyoderma
* no concurrent demodicosis
30
cyclosporine
* Immunomodulant
* suppresses T cells and cytokine production (IL-2)
* Life long therapy
* Initial dose: 5mg/kg SID
* Monitor for infections
* skin
* urinary
* efficacy not related to blood levels
* **drug interactions [cytochrome P450)**
* adverse effects
* GI, Papillomatous dermatitis
31
If a dog is on cyclosporin and needs ketoconizole
* **decrease cyclosporine because ketoconizole suppresses P450**
32
Papillomatous dermatitis
* side effect of cyclosporin
* reaction to staphyloccocus
33
Oclacitinib (Apoquel)
* new drug targets pruritus
* JAK inhibitor
* fast acting
* may precipitate demodicosis
34
IL-31 monoclonal antibody
* injectible, sc, 1X/month
* conditional approval
* Blocks IL-31
* best as adjunctive
* expensive
35
Antihistamines
* effective in 40-50% cases
* histamine not main mediator of AD in dogs!
* more effective for prevention, not treatment of pruritus
* try different types
* side effects
\*Benadryl dose: 1 mg/pound BID-TID
36
Different kinds of Antihistamines
* Diphenhydramine
* Benadryl
* Hydroxizine
* Atarax
* Chlorpheniramine
* Chlor-Trimeton
* Clemastine
* Tavist
* Trimepazine
* Temaril
* Amytriptiline
* Elavil
37
Good med for acral lick granuloma
* Amytriptiline
* antidepressant and antihistamine
* helps with the learned behavoir of acral lick
38
Essential Fatty acids
* Anti-inflammatory
* Barrier function
* restoration of normal lipid composition
39
Sources of essential fatty acids
* Linoleic acid (LA)
* alpha-linolenic acid (ALA)
* Dihomo-gamma - linolenic (DGLA)
* Eicosapentanoic acid (EPA)
Sources:
* cold water marine oil
* evening primrose
* borage
* black currant oil
40
Topical therapy
* frequent cold baths
* oatmeal
* topical anesthetic (e.g. pramoxine)
* Topical antihistamines
* Lime sulfur
* topical steroids
* capsaicin
* topical calcineurin inhibitors
41
Only use lymsulfur in....
a very greasy dog (I think)
42
Triamcinolone spray
Topical Steroids
* safe for long term use
* effective in 67% of allergic dogs
* Alcohol may be irritating
43
Hydrocortisone
topical steroid
* safe for long term use
* effective for mild to moderate cases
44
Capsaicin
* active ingredient of chilli pepper
* decreases substance P which mediates pain and pruritus
* initial worsening
* prolonged releif
* Used for localized pruritus
* lick granuloma
45
Tacrolimus
* Topical version of cyclosporin
* Topical calcineurin inhibitor
* minimally absorbed
* extremely safe
* effective for localized cases
* improvement in 1-2 weeks
* Initial burning sensation
46
Conclusion of AD
* Life long chronic disease
* Not curable
* Long term management
* importance of adressing concurrent diseases
* importance of combo therapy
