Dermatology - Atopic Dermatitis Flashcards
Atopic dermatitis, also known as allergic inhalant dermatitis, has a ______ predisposition.
familial (hereditary)
What are the major pathologic mechanisms associated with atopic dermatitis?
type I hypersensitivity and disruption/damage to the epidermal barrier
What is type I hypersensitivity mediated by?
IgE and subclasses of IgG
How does an animal become sensitized to an allergen?
An initial exposure to the antigen is required, then later exposure will lead to a reaction
What specific molecule plays a big role in pruritus due to atopic dermatitis?
interleukin-31
On a cellular level, what has been found in atopic patients?
they have been shown to have a cellular defect that allows increased adherence of bacteria to keratinocytes leading to increased bacterial infections
What allergens are known to cause atopic dermatitis?
pollens, molds, house dust mites, epidermals (wool, feathers, horse, human), insects, and many others (like tobacco)
What allergens typically appear in the spring?
trees and molds
What allergens typically appear in the summer?
grasses, and some weeds
What allergens typically appear in the fall?
weeds and molds
What allergens typically appear in the winter?
indoor allergens (dust mites, molds)
What allergens are typically year-round?
indoor allergens and combinations of the seasonal ones
At what age does atopic dermatitis typicall present?
9 months - 3 years of age
What is the hallmark of atopy?
pruritus
What are some signs of pruritus?
licking the feet, rubbing the fase, perineal pruritus, and generalized scratching
How do atopic lesions initally present?
mild: erythema, papules, and mild alopecia
What lesions are associated with chronic atopy?
lichenification, hyperpigmentation, and generalized alopecia
What areas are typically effected with atopy?
thin-skinned regions, such as the feet and between the toes, around the eyes, and in the axilla and inguinal regions
What is a common manifestation of atopy?
otitis externa
How may cats with allergic disease present?
they may have miliary dermatitis or other ‘reaction patterns of cats’ and generalized pruritus
What often perpetuates atopic dermatitis?
secondary infections
What secondary infections are commonly associated with atopic dermatitis?
superficial pyoderma and Malassezia dermatitis
What are secondary infections frequently the cause of?
apparent’ treatment failure of atopics: so-called ‘prednisone resistance’
Aside from secondary manifestations, otitis externa, and pruritus, what are some other clinical manifestations of allergy?
chronic anal sac inflammation and pruritus, acral lick dermatitis, and interdigital dermatitis
What are some diagnostic tools to diagnosing atopic dermatitis?
history, physical findings, dermatologic data base, allergy tests
What are the indications for allergy tests?
To confirm the diagnosis and to provide informtation for alternative therapy
What is intradermal skin testing?
Injection of known amounts of allergens intradermally and comparing the reaction to a positive (histamine) and negative control (saline)
What can be used for chemical restraint during intradermal skin testing?
only injalants, xylazine, dexdomitor, and some narcotis (no phenothiazines)
What is the technique for intraderma skin testing?
- Injections are made in the lateral thoracolumbar area after gentle clipping 2. No skin preparation 3. Area can be marked with a felt-tipped pen 4. Injection of 0.05 ml of antigen intradermally with a 25-gauge needle
When do you read the results from intradermal skin testing?
Reactions are read at 0, 15, and 30 minutes
How do you prepare a patient for intradermal allergy testing?
No antihistamines 1-2 weeks prior, no oral glucocorticoids for a minimum of 4 weeks, no injectable glucocorticoids for 1-3 months, no otic, topical, or opthalmic glucocorticoids for 2+ weeks prior, and no fatty acid supplements and/or off diets with high concentrations of fatty acids for 2 weeks prior
What is measured in intradermal allergy tests?
the degree of each reaction - erythema and wheal
What is a considered a positive result?
a reaction that is greater than 2+ on the scale of 0-4+
What is a 4+ on the scale?
histamine reaction
What does a positive result mean?
animal is allergic to antigen, allergen is irritative to the skin, and dermohraphia
What does a negative result mean?
animal is not allergic to the antigen, poor technique, drug inhibition, insufficient antigen as in mixed preparations, or an out-dated antigen
What techniques are used in serologic allergy tests?
radio-allergosorbent test (RAST) or ELISA techniques to measure allergen specific IgE levels in serum
False positives are common with what serologic allergy test?
RAST
With allergy testing, what must you ask yourself?
Do the test results fit the patients clinical features? And Do they make sense in correlation with severity of clinical signs, seasonality, and response to therapy?
What is the most important step to do first when treating atopic dermatitis?
control of perpetuating factors
What are the types of therapies for atopic dermatitis?
topical therapies, antihistamines, fatty acid supplements, glucocorticoids, cyclosporine, Oclacitnib, IL-31 Monoclonal andibody therapy, and/or hyposensitization
What is topical therapy indicated for?
to control the signs of allergies, especially pruritus
What are some topical therapies for atopic dermatitis?
colloidal oatmeal, colloidal oatmeal + others, topical glucocorticoids
How much relief does colloidal oatmeal allow for?
about 24-36 hours of relief from pruritus
What can colloidal oatmeal be combined with?
Diphenhydramine HCL, Pramoxine, and hydrocoritzone
Are topical glucocorticoids effective?
typically no, due to the generalized nature of the condition
Which topical glucocorticoid may be effective as an intermittent adjunctive therapy of atopic animals?
Hydrocortisone shampoo
What is the risk with overjudicious use of topical glucocorticoids?
it may cause iatrogenic hyperadrenocorticism and H-P-A supression leading to comedones, cutaneous atrophy at site of application, and calcinosis cutis
How often are antihistamines helpful?
in 15-30% of atopic animals - will reduce pruritus by 10-90%
What adverse effects are associated with antihistamines?
sedation, trembling, panting, or occasional excitement
What is the goal of using fatty acid supplements for atopic dermatitis therapy?
It is intended to promote production of non-inflammatory prostaglandins in lieu of those inducing inflamation - they are thought to modulate the arachidonic acid pathways, leading to production of prostaglandins and leukotrienes that competitively inhibit receptors
What percentage of patients have shown clinical improvement with fatty acid supplements?
15-30%
When are fatty acid supplements thought to be the most useful?
as adjunctive therapy when used in combination with either antihistamines or glucocorticoids
What type of glucocorticoids should be used for atopic dermatitis therapy?
only short acting oral glucocorticoids - prednisone, prednisolone, and methylprenisolon - long acting ones should not be used
What is the recommended protocol for using glucocorticoids?
give once daily initially to control clinical signs (1.1 mg/kg), then the dose is reduced and switched to alternate-day administration (1.1 mg/kg)
What is the recommended maintenance dosage for glucocorticoids?
0.5 - 1.1 mg/kg
What are the main side effects of glucocorticoid use?
polydipsia/polyuria, polyphagia, and panting
What is the generic name of cyclosporine that is used to treat atopic dermatitis?
Atopica and Atopica for cats
What is the goal of cyclosporine?
To control pruritus by regulating cellular mechanisms, thus repress activation of immune cell types known to be involved in atopic disease
What is the recommended dosage and protocol for use of cyclosporine?
5 mg/kg daily for induction 3-6 weeks, then either every other day or every day at 2.5 mg/kg
What is the success rate of using cyclosporine?
65-75%
What adverse effects are associated with cyclosporine?
vomiting, diarrhea, papillomatosis, and gingival hyperplasia
What are the disadvantages to using cyclosporine?
high cost of treatment, considered contraindicated in patients with neoplasia
What is the brand name of Oclacitinib?
Apoquel
How does apoquel work?
It is an IL-31 inhibitor, classified as a Janus-kinase-1 inhibitor
What remedies has Apoquel been shown to do?
reduce pruritus in animal models of atopy, in canine patients with atopic dermatitis, and in dogs with flea allergy dermatitis
Does Apoquel work quickly?
Yes, but it requires twice daily therapy for induction with once daily treatment for maintenance because it has a short duration of action
In what percentage patients is Apoquel effective?
in 70% of patients
What dogs should not get apoquel?
dogs under the age of 1
What adverse effects are associated with the use of Apoquel?
GI disturbances, weight gain, tendency to develop benign cutaneous masses
What drug is used for IL-31 monoclonal antibody therapy?
Cytopoint
How often is Cytopoint given and what does it do?
Once montly via injection and it is intended to bind to IL-31 before it can reach JAK-STAT receptors
What is the duration of action of Cytopoint?
The average is approximately 30 days, but can be longer in some patients
What is the advantage of using Cytopoint?
the advantage is that this therapy eliminates the daily fluctuations in drug concentrations that lead to variable effectiveness day to day
When is hyposensitization indicated?
if symptomatic therapy alone is ineffective, when the patient has unacceptable side-effects to symptomatic therapy, when the client chooses to treat the cause
What does hyposensitization appear to keep under control bettar than drugs that work by suppressing itch ?
it appears to be more effective at keeping perpetuating conditions under control than drugs that work by suppressing itch
What is the mechanism of action of hyposensitization?
Formation of IgG against the antigen to prevent cross-bridging of IgE bound to mast cells
How does hyposensitization work?
Antigen is induced in increasing doses to reduce sensitivity over time
What is the success rate of hyposensitization?
60-80%
How are antigens/allergens administered during hyposensitization?
typically subcutaneously, but can be given sublingually
What adverse reactions are associated with hyposensitization?
pruritus, wheals, urticaria, erythema, and anaphylaxis
What is the number 1 reason for atopic dermatitis ‘relapses’?
Malassezia dermatitis (not treated properly)
What are some other reasons for relapse?
inadequate doses, poor owner and patient compliance
When are you most likely to chose glucocorticoids for treatment?
When you need a rapid response, need anti-inflammatory effects, if it is needed seasonally or short-term, and if cost is a factor
When are you less likely to chose glucocorticoids for treatment?
concurrent health issues, patient cannot tolerate (historically), if you plan to allergy test
When are you more likely to chose cyclosporine?
Small dog (cause of cost), and some anti-inflammatory effect is desired and GCs aren’t an option
When are you less likely to chose cyclosporine?
concurrent infections, diabetes mellitus, cost is a factor
When are you more likely to chose Oclacitinib (Apoquel)?
need rapid response, prior to allergy testing, while waiting for immunotherapy, cost is somewhat a factor
When are you less likely to chose Oclacitinib (Apoquel)?
long term use, does not provide 24 hours of relief
When are you more likely to use Lokivetmab (Cytopoint)?
client compliance is an issue, convenience factor, adverse effects to other options
When are you less likely to use Lokivetmab (Cytopoint)?
clients are not mobile, large dogs (cost)
When are you more likely to chose immunotherapy?
younger dog, infectious/otitis are main manifestation, owners prefer to treat the disease vs masking symptoms
When are you less likely to chose immunotherapy?
Client compliance/ability to administer treatment, owners want/expect short term gratification
