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67 Cards in this Set
- Front
- Back
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DERMATOLOGY
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DERMATOLOGY
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What is the definition of canine atopic dermatitis?
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A genetically predisposed inflammatory and pruritic skin disease with characteristic clinical features associated with IgE antibodies, most commonly to environmental allergens
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What are the 2 findings in CAD dogs that make them susceptible?
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They have an impaired skin barrier function
They have a Th1/Th2 imbalance which favours IgE development |
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What is the most common allergen?
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House dust mites
also - food storage mites, pollens, human/cat dander, mould |
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How does the allergen get access?
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Mainly via the skin also via ingestion or inhalation
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What are the preformed inflammatory mediators?
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Histamine
Heparin Serotonin Proteinases |
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Platelet activating factor
Prostaglandins Thromboxanes Leukotriens These are all what? |
Newly generated inflammatory mediators
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Which breeds of dogs appear to have a much lower incidence of CAD?
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Poodles and mixed breed dogs
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When is the peak onset?
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Between 1 and 2 yrs.
Almost never below 3 months, rarely before 6mths or after 7yrs |
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What is the cardinal sign present in 99% of cases?
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Pruritus
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Where are the lesions?
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Mainly facial, ventral and pedal
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What is a common secondary sign?
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Otitis externa in 50% of cases
Affects the ear flap and vertical canal with the horizontal largely unchanged |
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What are some of the complications of CAD?
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Pyoderma
Bacterial overgrowth - exotoxin release, increased IgE Yeast Chronic skin changes |
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What are some important rule outs?
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Parasites
Food allergy - looks similar Contact allergy - macular/papular in hairless areas |
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How can CAD be tested for?
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Evidence of allergen-specific IgE through skin tests or in vitro tests
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Is a positive test diagnostic?
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NO!
Just supports a diagnosis |
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What is the cornerstone of therapeutic approach?
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Hyposensitisation (immunotherapy)
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What is the mode of action in immunotherapy?
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Via upregulation of Treg cells
The drugs (cyclosporin) take a while to work so are not indicated for short term use or old animals |
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When creating a vaccine how many allergens are mixed in?
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10
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What should happen is there is no response to therapy after 9 months?
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The patient should be reassessed
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What can you use along with immunotherapy?
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Low dose corticosteroids
NOT long acting injectables |
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How effective are antihistamines?
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In about 20-30% of cases as there are other mediators present
e.g. Hydroxyzine |
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What other medical therapies are available?
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Essential fatty acids
Misoprostal Cyclosporin A Interferon Use of shampoos and spot-ons that contain ceramides to increase skin barrier function |
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What types of food allergy are there?
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Hypersensitivity
Food intolerance |
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What signs can it present with?
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Dermatological - pruritus, papules, otitis externa
GI - Vomiting and diarrhoea Or both! |
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How can it be tested for?
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Intradermal skin tests
In vitro tests for allergen-specific IgE or IgG Hypoallergenic diet trial followed by provocation |
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How must the diagnosis be confirmed?
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By refeeding the original diet and waiting for a relapse w/in 14 days
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How can it be treated?
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Maintain on commercial hypoallergenic diet
Maintain on home-prepared diet - only if commercial ineffective, make sure is balanced Anti-inflammatory therapy - only if diet ineffective |
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What cells are involved and what type of hypersensitivity is contact dermatitis?
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Langerhans' cells = antigen presentation
Cell mediated (type 4) hypersensitivity |
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What are some of the signs?
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Restricted to hairless parts of the body
Maculopapular primary eruption Pruritis Hyperpigmentation and lichenification in chronic 2nd staph infection |
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If you cannot remove the source of the allergen what other things can you try?
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Oral or topical steroids
Pentoxifylline |
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What is Hymenoptera hypersensitivity?
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Severe allergic reaction to wasp, bee and hornet stings
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Where can angioedema (local swelling) be fatal?
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If in oropharyngeal region
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What drugs do you use for anaphylaxis?
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IV epinephrine with IV steroids
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What is Miliary dermatitis in cats?
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An erythematous papule that readily becomes encrusted.
Multiple lesions can be in any part of the body |
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What is one of the differentials?
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Lesions are very characteristic but larger lesions can look like pemphigus foliaceous
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What are some of the causes?
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Atopic dermatitis
Food allergy Lice Bacterial folliculitis Flea allergy |
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What diseases can cause a pruritus of the head and neck?
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Food allergy
Notoedres cati Pemphigus foliaceous |
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What are the features of an eosinophilic plaque?
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Well demarcated, raised, oozing and ulcerated plaques
Random distribution, often abdomen and medial thighs Highly pruritic Marked peripheral and tissue eosinophilia |
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Causes?
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Flea allergy
Food allergy Atopy Bacterial |
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What are the 3 forms of linear granulomas (collagenolytic granuloma)?
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Linear - posterior hindlimbs
Nodular - mouth Swelling on the chin |
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Which for has no other differentials as it is so characteristic?
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Linear form
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What is the aetiology of an eosinophilic (indolent) ulcer of the upper lip?
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Associated with allergy incl. fleas
May be bacterial/autoimmune component |
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How can you determine if the hairs on a cat have been pulled out by the cat or fallen out?
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The hair shafts will have shorn-off tips if they were bitten out
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What is the cardinal sign of Feline Atopic Dermatitis?
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Pruritus
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What can cats get that dogs don't?
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Concurrent feline asthma
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Cats can also show any combo of which?
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Self-induced hair loss
Miliary dermatitis Eosinophilic plaques Eosinophilic ulcers and linear granulomas |
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What is the most effective antihistamine in cats?
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Chlorphenarimine
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What has signs similar to atopic dermatitis and may also have GI signs?
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Feline food allergy
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Where are 33% of lesions restricted to?
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The head and neck
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True or False
Contact allergy is rarely seen in the cat |
TRUE
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What is the most common staph bacteria involved in pyoderma?
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Staph. pseudintermedius (formally Staph intermedius)
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Is S. pseudintermedius a true skin inhabitant?
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No it sits in carrier sites (nares, anus, genitals, buccal mucosa and conjunctiva) and waits for an opportunity
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What is normally present which protects the skin?
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Physical barrier of intact skin
Antibacterial substances in normal sebum Bacterial barrier of non-pathogenic bacteria |
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Resolution of pyoderma is accompanied by what?
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An inflammatory response, respponsible for the clinical signs
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What is the most useful classification of pyoderma?
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According to depth within the skin as it has direct bearing on treatment
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Pyotraumatic dermatitis and fold pyodermas are the 2 types of what?
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Surface pyodermas
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Pyotraumatic is seen as what?
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An itch-scratch-itch cycle
Erythematous, swollen, alopectic and exudative with rapid onset and pregression |
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What is another predisposing cause?
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Underlying perforating folliculitis - pyotraumatic folliculitis - needs aggressive abx
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Fold pyodermas present as what?
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Smelly and erythematous lesions within skin folds
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What are the types of superficial pyodermas?
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Impetigo - just under stratum corneum, readily seen pustule, benign usually, commonest in hairless areas
Mucocutaneous pyoderma - uncommon, GSD, swelling and erythema on lips Folliculitis |
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Why is the diagnosis so difficult in folliculitis?
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Starts out as a papule in the hair follicle but this phase is VERY short before it crusts over
Commonest form of bacterial skin infection |
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How can folliculitis be divided?
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Groin pyoderma in pubescent dogs
Moth-eaten "short-haired dog" pyoderma Spreading lesions with epidermal collarettes, alopecia, crusting +/- hyperpigmentation |
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Varying toxins by different strains of organisms and differing host response are the only two reasons for what?
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The varying manisfestations of folliculitis
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Folliculitis can spread and become what?
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Perifolliculitis
Hair follicle can also rupture leading to a nodular FB reaction from embedded keratin |
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What is Furrunculosis?
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Rupture of the hair follicle and spread of infection into the surrounding dermis
Often associated with demodicosis and may proceed to cellulitis |
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What is cellulitis?
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A deeper infection which spreads along the tissue plains, breaking out to the surface intermittently as discharging tracts
The deeper it is the more serious it becomes |
