Exam 2 - Canine Atopic Dermatitis Flashcards
what is canine atopic dermatitis?
genetically predisposed inflammatory & pruritic allergic skin disease with characteristic clinical features associated with IgE Ab most commonly directed against environmental allergens
pollen, mold, dander, mites, insects, & foodstuffs
what is canine atopic-like dermatitis?
inflammatory & pruritic skin disease with clinical features identical to those seen in canine atopic dermatitis in which an IgE response to environmental or other allergens cannot be documented
T/F: it is estimated that 10-15% of animals have canine atopic dermatitis
true
what breeds are predisposed to canine atopic dermatitis?
terriers, spaniels, bulldogs, dalmatians, & sharpeis
what is the age of onset seen in dogs with atopic dermatitis?
0.5-3 years old
T/F: in a dog with atopic dermatitis, if there are no underlying infections, it will have an excellent response to steroids for treating the pruritus
true
what are some clinical signs that may clue you in to canine atopic dermatitis?
itch, recurring to chronic skin/ear infections, self-traumatic hair loss, & odor
the lesion distribution is commonly seen in what skin disease?
canine atopic dermatitis
how is canine atopic dermatitis diagnosed?
there is no reliable test that can differentiate it from other pruritic inflammatory conditions, so the diagnosis is based on history, clinical signs/findings, & the exclusion of other differential diagnoses
when is allergy testing used as a tool for patients with canine atopic dermatitis?
identifying offending allergens for inclusion in immunotherapy in atopic patients with a compatible history & clinical signs for more than 6 months out of the year
what are the favrot clinical criteria that are used for a clinical diagnosis of canine atopic dermatitis?
onset under 3 years of age
mostly indoor dog
steroid responsive pruritus
chronic or recurring yeast infections
alesional pruritus at onset
front paws affected
pinnae affected
what is the pathophysiology of canine atopic dermatitis?
sensitization - allergens are absorbed & epidermal langerhans cells capture/uptake/process it & takes it to regional lymph nodes as an antigen presenting cell to t cells
CD4 Th2 cells proliferate & secrete IL-4, IL-5, & IL-13 which induce B cells to produce IgE antibodies
re-exposure - allergen-specific IgE bound to LC capture/uptake/processing & then are presented to allergen specific T cells
CD4 Th2 cells proliferate & secrete IL-4, IL-5, IL-13, IL-31 (pruritogenic cytokine) which induces b cells to produce IgE antibodies & mast cell activation
what is ASIT?
practice of administering gradually increasing quantities of an allergen extract to an allergic subject to ameliorate the symptoms associated with subsequent exposure to the causative allergen
why are allergy tests used?
to select candidate allergens for immunotherapy & to institute allergen avoidance strategies
T/F: no allergy test is completely sensitive or specific & can just reflect allergen exposure in normal patients
true
T/F: allergy tests are screening tests for allergies in pruritic dogs
false - not screening tests
what is intradermal testing? how is it used for patients with atopic dermatitis?
process of introducing antigens into the dermis of atopic patients to elicit macroscopic hypersensitivity reactions - a positive challenge can manifest as an immediate-phase reaction or a late phase reaction
doesn’t diagnose it but it can help support the presence of atopic-like dermatitis with a negative test
what are some indications for pursuing intradermal testing for patients that are suspected to have canine atopic dermatitis?
after you have a clinical diagnosis of CAD established
used to support diagnosis
patient has persistent signs over 6 months
used to select allergens for immunotherapy
owner is willing to administer immunotherapy
what is allergen-specific IgE serology?
blood allergy test - process by which allergen-specific IgE is identified & quantified in the serum of a patient suspected of being affected with atopy
once atopic dermatitis has been confirmed in your patient, how is ASIT used? how long does it take?
retrain the immune system in your patient that has signs that occur greater than 6 months out of the year
or if symptomatic therapy isn’t tolerated or effective
may take 6-12 months to take effect
what is hypersensitivity?
objectively reproducible clinical signs initiated by exposure to a defined stimulus as a dose tolerated by normal dogs
what is an allergy?
hypersensitivity reaction initiated by a specific immunological response to an allergen & mediated either by antibodies or cells
what is an allergen?
antigen that favors the development of a hypersensitivity response
what is atopy?
genetically predisposed tendency to develop IgE-mediated allergy to environmental allergens
what is atopic disease?
any clinical manifestation of atopy - in the dog, atopic dermatitis is most commonly diagnosed
how is canine atopic dermatitis characterized?
characterized by t-cell dysregulation often beginning as a typical type I hypersensitivity reaction (IgE) with progression towards a type IV hypersensitivity (cell-mediated) cellular infiltrate over time
what cells are at the root of pathology in canine atopic dermatitis?
t lymphocytes
what is the key cytokine present in canine atopic dermatitis? why?
IL-31
IL-31 is the cytokine that binds to the JAKS receptor which is what triggers the sensation of itch
what is the role of janus kinase enzymes?
intracellular signaling enzymes that function in cell communication with many cytokines signaling through JAK (IL-31)
what role do janus kinase enzymes play in the sensation of itch?
IL-31 binds to their receptors - JAKS enzymes stimulate the phosphorylation of STAT which causes downstream effects of turning on pro-allergic/inflammatory genes to propagate the allergic response
what are the 5 F’s in regards to lesion distribution of canine atopic dermatitis?
face, feet, folds, flexure surfaces, & friction surfaces
what are the 2 phases of therapy when approaching a patient with atopic dermatitis?
reactive therapy - induction of the clinical sign remission to stop the flare, depending on the degree of clinical signs, glucocorticoids or oclacitnib
proactive therapy - prevention of clinical sign recurrence to reduce relapses, dependent upon the degree of clinical inflammation: allergen avoidance, immunotherapy, proactive use of drugs
why does topical therapy help patients with canine atopic dermatitis?
removes the allergens & microbial agents & improves epidermal barrier function
how do glucocorticoids work for dogs with atopic dermatitis?
they suppress innate & cell-mediated immunity
what is the MOA of oclacitnib?
specifically targets & inhibits IL-31 mediated janus kinase activity (JAK1) resulting in diminished pro-inflammatory cytokine & enzyme activity
how does lokivetmab work for dogs with atopic dermatitis?
caninized monoclonal antibody that binds to IL-31 rendering it non-functional
what is the intended goal of immunotherapy when treating canine atopic dermatitis?
not to eliminate or cure signs because it won’t but to reduce the extent & severity of signs
what is the suggested MOA of ASIT?
largely unknown, but we think it induces t regulatory cells to produce IL-10 (anti-inflammatory), reduce IgE production, & produce IgG blocking antibodies to quench the allergen
atopic dermatitis is a disease suspected to be caused by ______ _________ & a faulty __________ __________
cytokine dysregulation
epidermal barrier
atopic dermatitis is the second most common allergic canine skin disease - what is the first?
flea allergy dermatitis
what is important about CD4 Th2 cells in dogs with atopic dermatitis?
atopic individuals have a skewed proportion of Th1:Th2 cells favoring the Th2 subtype & less immunosuppressive TGFb
what is the griffin clinical criteria used for canine atopic dermatitis?
suggestive - history & PE findings with pruritus present in areas other than the dorsolumbar region
compatible - pruritus in one or more of the following: face, pinnae, axillae, flexor elbow, flexor carpus, extensor tarsus, & paws
tentative - compatible criteria plus the exclusion of major differentials
definitive - tentative criteria plus positive intradermal or serologic test to one or more non-insect aeroallergens
what are the 2 main parts of the development of canine atopic dermatitis?
sensitization - animal is becoming allergic & Th2 lymphocyte polarization occurs
re-exposure - clinically allergic animal that has cytokine dysregulation
cytokine dysregulation in dogs with atopic dermatitis causes mass release of what cytokines?
IL-2, IL-4, IL-5, IL-6, IL-13, & IL-31
T/F: stimulated Th2 lymphocytes release pro-inflammatory cytokines in clinically allergic dogs with canine atopic dermatitis
true
what cytokine plays a key role in neuronal stimulation in atopic dermatitis?
IL-31 - key component of ongoing pruritus & inflammation
what are the absolutes of management in a dog with canine atopic dermatitis that is often neglected?
identifying & eliminating infections
flea control
topical therapy
what dosing is used for lokivetmab for dogs with atopic dermatitis? is it useful for seasonal & non-seasonal dermatitis?
dose based off of product insert ~2mg/kg given SQ every 4-8 weeks
works for both seasonal & non-seasonal
what dosing is used for oclacitnib for dogs with atopic dermatitis? is it useful for seasonal & non-seasonal dermatitis?
apoquel 0.4-0.6mg/kg by mouth every 12 hours for 2 weeks & then every 24 hours
what dosing is used for cyclosporine for dogs with atopic dermatitis? is it useful for seasonal & non-seasonal dermatitis?
5mg/kg by mouth every 24 hours for 4-6 weeks & then tapered to every 48 hours thereafter
used for non-seasonal atopic dermatitis in animals that have had a poor response to other therapies
T/F: steroids are not ideal for chronic use when managing a patient with canine atopic dermatitis
true
what dosing is used for prednisone for dogs with atopic dermatitis? is it useful for seasonal & non-seasonal dermatitis?
0.5-1.0mg/kg by mouth every 24 hours for 7 days & then taper to the lowest effective dose every 48 hours
used for seasonal atopic dermatitis
