Derm 2: pruritis & allergies Flashcards
the age of onset of pruritis from atopic dermatitis is ______, while pruritis from food allergies often develops when they are _____. Parasites can affect any age of dog but are most common in _______ dogs. Allergies are typically _____ while scabies is more ______. If other animals or people in the house are pruritic too, _____ differentials should be prioritized.
1-3 years old, less than 1 year old, younger, contagious
(although his powerpoint says to watch out for food allergies in older dogs >5 years old in an atopic dog)
older dogs; consider immune-mediated, endocrine, neoplastis
what are the general causes of pruritis?
Allergies, parasites, infectious, immune-mediated, neuropathic, neoplastic
All People In Icy Norway Navigate (APIINN)
why is figuring out seasonality of pruritis important?
one of the only pieces of hx that will help you diagnose atopy vs food allergy (other is response to food trial)
tell me about your ddx for pruritis in a dog that responds to these medications:
1) apoquel
2) cytopoint
3) steroids
4) Atopica
1+2 = more specific to allergic itch
3+4 = affects immune system more broadly
what body distribution pattern does this condition have: flea allergy
caudal dorsum/tail base, neck, inguinal
what body distribution pattern does this condition have: scabies
pinnal margins, elbows, hocks, ventrum
what body distribution pattern does this condition have: demodex
paws, head/face, can be haphazard
what body distribution pattern does this condition have: pediculosis and Cheyletiella
dorsum
what body distribution pattern does this condition have: staph pyoderma
dorsum, inguinal region
what body distribution pattern does this condition have: yeast dermatitis
varies
periocular, muzzle, paws, ventral metacarpal and metatarsal regions, perianal, inguinal, axillary, cubital fold
what body distribution pattern does this condition have: atopic dermatitis or food allergy
varies
periocular, muzzle, paws, ventral metacarpal and metatarsal regions, perianal, inguinal, axillary, cubital fold
what condition has this distribution?
flea allergy
what condition has this distribution?
Pediculosis or Cheyletiellosis
what condition has this distribution?
scabies
what condition has this distribution?
demodex
what condition has this distribution?
yeast dermatitis or canine atopic dermatitis
what condition has this distribution?
canine atopic dermatitis or yeast dermatitis
tell me a general clinical approach to dealing with pruritis
- thorough history
- cytology, ringworm testing, skin scrapes
- treat any infections (skin and ear)
- provide itch relief
- provide treatment to rule out ectoparasites (isoxazolines)
- strict hypoallergenic diet trial and follow up on infection in 4 weeks and food trial response in 8 weeks
be more aggressive diagnostically and consider biopsy when systemic signs are present, lesions are unusual, and when neoplastic or immune-mediated disease is suspected
What is Canine Atopic Dermatitis?
inflammatory and pruritic disease with typical clinical signs associated with IgE production directed most commonly against environmental allergens
food-induced atopic dermatitis (food allergy) and CAD are now considered by many to be the same disease
tell me about the pathogenesis of atopy (canine atopic dermatitis)
not completely understood
all the following factors play a role: sensitization to allergens, immune system dysfunction, skin barrier abnormalities, alterations in microbial populations, environment, genetics
tell me about the genetics involved with canine atopic dermatitis
risk: 2 atopic parents > 1 atopic parent > no atopic parents
up to 50% of risk of developing atopic dermatitis is from genetics
many candidate genes involving cytokines and skin structural proteins
tell me about environmental and other risk factors for developing canine atopic dermatitis
urban environment, male, neutered, allowed on upholstered furniture, receiving flea control, exposure to smoke, being raised in a shed as a puppy, adopted at 8-12 weeks, living in a county with a vet dermatologist, regular bathing, chocolate labs vs other color labs
potential protective factors: rural, walking in woodlands, fields, or beaches, non-commercial diet, raw diet, living with other animals
tell me about IgE and testing atopic dogs via serology or intradermal skin testing (IDST).
IgE to environmental allergens is demonstrable in most but not all atopic dogs with serology or IDST. but there is no increase in total IgE in atopic vs normal dogs. Not all atop dogs demonstrate allergen specific IgE. Non-atopic dogs also often demonstrate allergic specific IgE
tell me about common environmental allergens associated with Canine atopic dermatitis
dust mites is most common
CAD dogs are frequently sensitized to grass pollen, weed pollen, tree pollen, and molds
pollen allergies is commonly a reason for seasonality in CAD.
what cytokines are involved with CAD?
IL31, IL17, IL33
im not fucking learning more than this
what is the primary route of allergen contact with CAD? why is this important?
percutaneous absorption
a defective skin barrier can lead to increased allergen penetration and exposure. dysfunction of the skin barrier is a factor in CAD.
tell me about skin microbiota and CAD
microbiota of canine atopics is less diverse than normal dogs with an increased prevalence of Staph spp.
CAD dogs are prone to Staph and Malassezia infections of skin and ears.
clinically, tx of bacterial and yeast infection in atopic dogs results in notable improvement, though organisms aren’t completely eliminated from skin (tx may normalize bacterial pops)
how do you diagnose CAD?
Hx + C/S + dx of exclusion
there is no way to definitively diagnose CAD
3 components:
1. rule out other skin conditions that resemble CAD –> full hx + PE, derm PE, ectoparasite exam, skin cytology, fungal culture, elimination diet trial (use clinical judgement)
2. detailed interpretation of historical and clinical features of condition –> use Favrot’s criteria
3. assessment of skin reactivity be intradermal testing of IgE detection by serum
what are the C/S of CAD
hallmark = Pruritis!!!
primary lesions vary, can include: erythema, erythematous papules
most are secondary lesions: alopecia, excoriations, lichenification, secondary infection
common body sites affected: perioral, periocular, axillae, inguinal, cubital fold, distal limbs & paws, ventral neck, perianal, pinnae, external ear canals
there is some breed variation on body site location but I dont wanna memorize them.
progressive disease… initial symptoms may be mild and seasonal, progressing to pruritis and secondary manifestations that are non-seasonal.
tell me about Favrot’s criteria.
presence of 5 out of 8 of these things is 85% sensitive and 79% specific to CAD.
- age at onset <3 years
- mostly indoor
- corticosteroid-responsive pruriti
- chronic or recurrent yeast infections
- affected front feet
- affected ear pinnae
- non-affected ear margins
- non-affected dorso-lumbar area
food-induced and non-food-induced are indistinguishable using this method, so diet trial still necessary.
How can you use serum IgE or intradermal testing with CAD?
NOT FOR DIAGNOSING CAD!!! USED FOR IDENTIFYING OFFENDING ALLERGENS FOR AVOIDANCE OR IMMUNOTHERAPY!!!
these tests are not useful for IDing food allergens
IDAT is considered gold standard, but evidence shows that there is no superior test between the two. IDAT is less available and requires drug withdrawals, whereas serum is widely available (but different labs show different results which isn’t good)
basically, allergy tests are used for 2 reasons:
1. to ID any allergens that can be avoided
2. allows the formulation of prescription for allergen-specific immunotherapy (ASIT)
tell me about food-induced CAD. when a food allergy is present, what is the usual source? how do you diagnose a food allergy?
protein is usual source (chicken, beef, fish most commonly)
clinically see dogs with atopic signs that improve but don’t resolve with an allergy diet.
only way to diagnose food allergy is by well-executed diet trial.
what are the steps of a diagnostic diet trial?
- choose food trial —> hydrolyzed (protein particles become too small to be allergen), limited ingredient, novel protein source
- feed trial diet for at least 8 weeks –> make sure that this is the ONLY food that is being consumed!
- recheck in 8-12 weeks and confirm food trial was completed –> confirmation involves re-feeding original diet and seeing if C/S come back.
often, you are treating the pruritis and secondary infections while trial is going on. It’s important to stop pruritis treatment for awhile (1-2 weeks) during the trial to see if it subsideds on the new diet.
what are the 4 main medical therapies for treatment of pruritis?
glucocorticoids
modified cyclosporine (atopica)
oclacitinib (apoquel)
lokivetmab (cytopoint)
what is the mechanism of action of oclacitinib (apoquel)?
Janus kinase inhibitor
targets JAK1 cytokines, which are key in signal transduction of pro-inflammatory, pro-allergic, and pruritogenic cytokines.
works on normal immune function activity too
leaves JAK2 cytokines alone
how do you use oclacitinib (apoquel)? like are there side effects, when do you administer, how long to administer, etc
BID for 14 days, then once daily. can be used longterm. rarely associated with serious adverse effects, well-tolerated.
very fast acting
only for use in dogs >12 mo
do not use in dogs with serious infections, evidence of immune suppression or evidence of malignant neoplasia, nor in breeding, pregnant, or lactating dogs.
not labelled for cats, but can be given for allergy cats at higher doses than dogs.
there is no increase of cancer risk with long term apoquel
if admin is stopped, symptoms will come back
what is the mechanism of action of lokivetmab (cytopoint)?
caninized anti-IL31 monoclonal antibody
highly specific to IL31, doesn’t have activity on normal immune function
how do you use lokivetmab (cytopoint)? like are there side effects, when do you administer, how long to administer, etc
Subq injection q 4-8 weeks
doesn’t impact normal immune function, can be given at any age, can be given with infections/malignancies/etc
DO NOT GIVE TO A CAT!! or any other species other than a dog
if you discontinue drug, symptoms will return
what is the mechanism of action of cyclosporine (atopica)?
calcineurin inhibitor –> immunosuppressive
how do you use cyclosporine (atopica)? like are there side effects, when do you administer, how long to administer, etc
oral, once daily for 4-6 weeks
slower acting, not useful for flare-ups
can eventually be given every other day or weekly
adverse reactions are very common (v+, d+ most commonly, gingival hyperplasia and hypertrichosis can be seen). these are transient, mild to moderate, usually don’t require drug discontinuation.
don’t use if hx of malignancy or infection
careful when using in cats, bc they harbour infections (FIV, FeLV)
dogs >6mo
how do you use corticosteroids? like are there side effects, when do you administer, how long to administer, etc
effective in rapidly reducing pruritis and inflammation
prednisone 0.5mg/kg once to twice daily for several days, then tapered.
side effects are common and proportionate to dosage (PU/PD, polyphagia)
best used in short term, longer term = more adverse effects (weight gain, alopecia, muscle atrophy)
cats require higher doses, use prednisolone instead of prednisone
don’t use long-acting injectable steroids (like depomedrol) in treating atopic dermatitis (reserve for last resort)
topical steroids can be used for localized pruritis, short term
tell me about the use of antihistamines with CAD
antihistamines have limited efficacy in chronic atopic dermatitis. better to use for preventative treatment in dogs with only mild skin lesions.
tell me about allergen specific immunotherapy (ASIT) in regards to atopic dermatitis
patients requiring chronic antipruritic therapy are good candidates for ASIT. it’s the only treatment that can modify or reverse the disease, may also prevent progression of the disease (should be considered early).
administering gradually increasing quantities of an allergen to ameliorate the signs associated with exposure to the allergen.
improvement can take 3-9 mo, can take 12 mo or even longer to see full benefit
ASIT should be given for live if effective
can be injectable or oral
side effects include pruritis, serious side effects are rare
this is a referral procedure
what are the 4 goals of topical therapy in allergic dogs? how do you achieve each goal?
- remove allergens from skin –> physical act of bathing or wiping skin
- treat and prevent secondary infections –> chlorhexidine with or without antifungals (shampoo, sprays wipes, etc)
- restore skin barrier –> repair skin barrier with topical products (limited evidence that this works but there’s really no downside to trying)
- deliver anti-itch ingredients –> topical products that contain anti-itch ingredients (colloidal oatmeal, moisturizers, etc)
you have a patient named Zoink! (credit to ChatGPT) newly diagnosed with canine atopic dermatitis. Tell me a chronic treatment plan for this dog and what you’ll tell the owner
Firstly, make sure the owner knows that this is a life-long disease and that you will be chronically treating.
- itch relief –> oclacitinab, cytopoint, or cyclosporine
- prevention of infections –> twice weekly bathing with chlorhexidine/azole anti fungal shampoo
- other topical treatments for problem areas (ex. antimicrobial wipes for paws, otic steroids for otitis)
- explore immune system mod with ASIT and avoiding allergens
- specialized diets and treatments to repair skin barriers –> consider this
- ID and avoid dietary allergens –> diet trial!
You have a patient named Splat who has canine atopic dermatitis. He is presenting for an acute flare. Tell me how to treat the acute flare.
- check for parasites and secondary infection –> treat when present
- provide fast-acting itch relief –> oclacitinib, lokivetmab, or glucocorticoids
- probe for dietary indiscretion in an animal with known food allergy or consider a hypoallergenic diet
- if allergens are known, consider if signs could be related to exposure to allergens and eliminate exposure, or consider ASIT
