2/3. Canine Atopic Dermatitis

What is an allergic response to allergens causes inflammation of the skin?

Atopic Dermatitis

What is an itching sensation or feeling?

Pruritus

What is an allergic disease of the skin, gastrointestinal and respiratory tracts?

Atopic Syndrome

What are the THREE body systems that allergic disease can cause problems in?

skin, gastrointestinal and respiratory tracts

What is usually affecting more than skin alone with Atopic Syndrome?

Hypersensitivity

What is the prevalence of atopy in dogs and cats?

10-15%

T/F Atopy can affect horse, cattle, small ruminants, swine, avian, exotics, wildlife

True

What is the process of atopy in animals? (5 steps)

1. initial allergen exposure

2. recognition by antigen processing cells (APCs)

3. Presentation of antigens by the APCs to lymphocytes

4. Ig produced at regional lymph nodes

5. Triggered mass cell degranulation and proinflammtory cytokine released upone re-exposure

What is the initial allergen exposure primarily?

percutaneous

How is the initial allergen exposure in horses?

inhalant

What is the unique APC of the dermis?

Langerhan Cells

What lymphocyte is used to cytokine production thus leading to stimulation of leukocytes?

T Cells

What lymphocyte is used for antibody production?

B cell

What is the primary immunoglobulin that is present in Atopy?

IgE

Which T helper cell response is seen more in Atopy?

Th2

Atopy is a _____ mediated disease

cytokine (•IL-4, -5, -13, -10 and many others!)

The target therapy for atopy (ex: Apoquel®, Zenrelia®, Numelvi®, Cytopoint®, Befrena) targets what cell?

Th2

What is the cycle of Atopic Dermatitis?

1. Abnormal skin barrier

2. increased allergen exposure

3. Sensitization

4. Dermatitis

5. Pruritus

In order to treat atopy, what must you do?

break the itch cycle AND restore barrier function

Industrialization, urbanization and Westernized lifestyle have a devastating impact on the epithelial barriers of the skin, airways and gut mucosa, as proposed by what theory?

The Epithelial Barrier Theory

What is the etiology of atopic dermatitis?

Genetic tendency → abnormal skin barrier + overactive immune response.

What is the Etiopathogenesis of atopic dermatitis? (5 steps type or read)

1. Skin barrier is defective → allergens (pollen, dust mites, etc.) can enter the skin more easily.

2. The immune system reacts to these allergens.

3. IgE and inflammatory cells are activated.

4. Inflammation causes itching (pruritus).

5. Scratching damages the skin further → more inflammation and sometimes secondary bacterial/yeast infections.

6. This creates an itch-scratch cycle.

If the atopic dermatitis is very bad, what are TWO organ systems/spaces to be concerned about?

CNS, joints

What happens as soon as the inflammation of the skin occurs with atopic dermatitis?

Cutaneous Dysbiosis

What are the names of the bacteria that is seen on the skin during infection?

- Staphylococcus pseudintermedius,

-Malassezia pachydermatis

What are the names of the bacteria that is seen on the ears during infection?

- S. pseudintermedius

- M. pachydermatis

- S. schleiferi

- Corynebacterium sp.,

- Pseudomonas sp.

What contributes to dysbiosis? (5)

•Alteration of skin barrier function

•Alteration of antimicrobial peptides

•Alterations of humidity, pH, and temperature

•Upregulation of adherens proteins (e.g., fibronectin) on keratinocytes

•Downregulation of tight junctions between keratinocytes in inflamed skin

When there is dysbiosis of the skin, what alteration do you see in the skin barrier?

Decreased lipids

What happens when there is an upregulation of adherens?

•Bacteria and yeast stick better

What TWO things happen when there is a downregulation of tight junctions between keratinocytes in inflamed skin?

•Things sneak through more easily

•Increased skin permeability

Why does it matter if there is dysbiosis?

•Infections make inflammation worse

•Anti-pruritic therapies cannot mask it all!

•Topical therapy restores cutaneous bacterial and fungal diversity and improves dermatitis

What are some dog breeds that are predisposed to atopic dermatitis? (there is alot)

•West Highland White terrier, Yorkshire terrier, pitbull terrier, terrier, terrier

•Bulldogs (English and American)

•Retrievers: Labrador and golden

•Doodles

•Boykins

•German shepherd dogs

•Setters: Irish, English

•Beagle

•Miniature Schnauzer

•Lhaso Apso

Dalmations

What are some predisposing factors of Atopic Dermtitis? (again alot)

•Environment

•Geographic location

•Diet

•Genetics

•Hygiene

•Concurrent illnesses

•Early life sensitization

•Hormonal influences

•Unknown factors??

When is the age of onset for greater than 50% of atopic dermatitis?

6 months - 3 years

You rarely see a dog greater than 7 years old with a new allergy, when does this sometimes happen?

•moving to new geographic area

What is the hallmark sign of atopic dermatitis?

PRURITUS!!!

What are some other clinical signs of atopic dermatitis?

•Erythema

•Alopecia

•Scaling - seborrhea

•Excoriations

•Hyperpigmentation

•Lichenification

•Papules

What are some non-cutaneous clinical signs of atopic syndrome?

•Allergic conjunctivitis

•Allergic asthma

•Reverse sneezing, rhinitis

•Lethargy and irritability

Gastrointestinal signs (rare)

What THREE things make cats unique when it comes to atopic dermatitis?

- Eosinophilic Granuloma Complex/Syndrome

- Rodent/indolent ulcer

-•Linear granuloma

When cats become infected with atopic dermitits, what is seen along the ventral abdomen, dorsal neck, head and is super itchy?

Eosinophilic plaque

What is a unique atopic dermatitis sign in cats that is seen on the upper lip?

Rodent ulcer

What unique atopic dermatitis sign in cats is seen on the lateral caudal thighs, mouth and is not itchy?

linear granuloma

Maybe FYI moment... when you are looking at granuloma's in the cat, how can you assume that it is eosinophillic and why?

there is a pale center due to the dumping of degranulated goo from the eosinophils

Where on the body will you see atopic dermatitis most commonly? (7)

•Ventrum and axilla

•Flexor surfaces - elbow, tarsus

•Extensor surfaces - carpus

•Feet

•Face

•Ears

•Perianal +/- anal sacculitis

T/F Severe and chronic cases of atopic dermatitis can show lesions anywhere

True

check out the pictures on slide 32 if you like pictures that show you where theyre gonna be itchy

or dont thats chill

How do you diagnose atopic dermatitis?

diagnosis of exclusion (history is very important)

When getting a history, what are some important questions/ things you ask about to help you limit down the derm DDX?

• Age of onset

• Seasonality

• Familial history

When is the majority of atopic dermatitis cases are typically seen?

spring, fall

T/F You must RULE OUT everything else that causes pruritus to limit down to allergies

True

Here are some things that can make a dog itch that is not allergies!

•Ectoparasites - flea, Sarcoptes, Demodex

•Food allergy

•Flea allergy

•Secondary infections: bacteria, yeast, dermatophyte

•Irritants

•Seborrhea sicca secondary to other conditions

•Autoimmune disease?

•Neoplasia?

amazing perfect great

What is the number 1 reason why the atopic dermatitis cases will come to you?

because the owner is tired of how itchy the patients are

What is the pruritus threshold affected by?

•Allergen load

•Skin irritants

•Other diseases

•Infections

•Weather

•Altered epidermal barrier

•Emotional state

T/F With the pruritus threshold, you have to address all of the things that are causing itch

False, Address enough, not all, causes of pruritus for best response

What is the gold standard for treating allergies in animals?

•Allergen-specific Immunotherapy (ASIT)

What are some other things that you can do to treat allergies?

•Allergen exposure avoidance

•Anti-inflammatory therapies

•Anti-pruritic and immunomodulatory therapies

•Behavioral-modulating therapies

•Nutrition and supplements

When is allergen exposure avoidance an unreasonable for treatment of atopic dermatitis?

when it is an environmental allergy

What is the most specific treatment that targets and reprograms the immune system for allergies?

ASIT

How does ASIT improve the immunologic tolerance?

•↑ __ _____ activity

•↑ IgG4 blocking antibody

•↓ mast cells & _____ release

•↓ pro-inflammatory ____ release

•↓ systemic inflammation

- T suppressor

- histamine

- cytokine

What T cell does ASIT upregulate and downregulate?

Th2- downregulate

T reg- upregualte

What are TWO things that you can do to identify the most likely allergens?

•Intradermal test

•Serology

After you identify the allergen, what must you formulate to help the allergies?

immunotherapy

How would you describe the hypersensitivity of ASIT?

IgE-mediated Type I hypersensitivity

Jumpscare moment, what is a type 1 hypersenitivity?

Type I hypersensitivity = an immediate allergic reaction

What are some downfalls to ASIT?

- expensive

- requires sedation

What is "atopic-like" dermatitis?

when the hypersensitivity is not IgE ( the skin and blood test negative)

Where do you inject an ASIT test in horse?

side of the neck

What is first injection (positive control) of the ASIT and what grade would it be?

histamine, grade 4

What is the second injection (negative control) of ASIT, and what is the grade?

saline, 0

What are the THREE parameters of subjectivity for ASIT?

1. wheel side

2. turgidity- firmness

3. erythemia

T/F Cats do not do Type 1 reactions well so the skin test is harder to read

True

What ASIT test is not clinical response test and quantifies IgE in circulation?

Serology

What are some pros to using Serology over Skin test?

•Convenient, fast, no sedation

What are the six formulation guidelines for ASIT?

-history

- environment

- cross reactivity

- 10-12 allergens

- multi-vital therapy

- separate mode

go look at •Induction vs Maintenance :) sorry

okay

What are THREE adverse effects of ASIT?

•Local reactions - antihistamines

•Severe exacerbation of clinical signs - reduce dose

•Anaphylaxis - Epi/supportive care

What are some of the routes that ASIT can be given?

•Subcutaneous

•Sublingual

•Intralymphatic (less common)

•Adjuvanted (less common)

•Transdermal (super new)

FOR REFERENCE:

SLIT = Sublingual = under the tongue

SCIT = Subcutaneous = under the skin

OKAY perfect

How often do you have to give SLIT?

once-twice daily lifelong

How often do you have to give SCIT?

once weekly lifelong

T/F Complete avoidance of allergies is impossible

True

How can you aid in avoiding allergens?

•Reduce house dust mites

•Reduce storage mites

•Frequent bathing - once weekly

What is a behavioral modifying medications and pain medications that is used for anti-inflammatory therapy?

Antihistamines

What are some other anti-inflammatory therapies?

•Essential fatty acids

•Supplements (Redonyl®, Dermaquin®)

•Glucocorticoids

•Immune-modulatory medications

rapid fire conclusion!!!

Atopic dermatitis is a ____-____ pruritic disease

It affects _____ adults and ____ species

It is a diagnosis of _____

and the treatment is ______

life-long, young, all, exclusion, multimodal

What is the the treatment for the primary disease of atopic dermatitis?

immunotherapy