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Dermatology > Allergic skin disease > Flashcards

Allergic skin disease Flashcards

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Dermatology Board Prep flashcards
1
Q

What are the 4 main allergic diseases which affect the skin?

A
  • Urticaria/angioedema
  • Atopic Dermatitis (AD)
  • Food Hypersensitivity
  • Insect Hypersensitivity
  • (Contact Allergy)
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2
Q

What mechanism underlies urticaria and angioedema?

A

Commonly involves IgE mediated type 1 immediate hypersensitivity leading to focal oedema. Common problem in the horse

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3
Q

What mechanisms underlies atopic dermatitis (AD)?

A

chronic inflammatory skin disease with features of both cell-mediated and IgE-mediated hypersensitivity and characterised by pruritus. Common in dogs, less common in cats and horses.

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4
Q

What are the similarities between hypersensitivity disease and allergic disease? 3

A
  • objectively reproducible signs
  • exposure to a defined stimulus
  • at a dose tolerated by normal individuals
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5
Q

What are the differences between hypersensitivity disease and allergic disease? 3

A
  • HYPERSENSITIVITY = no allergic immunologic mechanisms (e.g. idiosyncratic metabolic or pharmacologic mechansim) OR unknown mechanism
  • ALLERGY = initiated by immunologic hypersensitivity (state of heightened reactivity to Ag), known allergic mechanism
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6
Q

T/F: allergic inflammation produces tissue injury

A

True

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7
Q

T/F allergic disease can be induced/aggravated by non-immunological factors (infection, exercise etc)

A

True

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8
Q

Define Urticaria

A

Multiple wheals (hives). Circumscribed raised lesions caused by dermal oedema

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9
Q

Define Angioedema

A

marked localised SC oedema. Strictly a sign, not a disease

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10
Q

What is the principal effector cell in urticaria and angioedema?

A

Mast cell. MC activation can be:

  • IgE dependent (classical type 1 allergy)
  • IgE independent - other immunologiccal mechanisms such as complement or non-immunological mechanism
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11
Q

Features of urticaria/angioedema

A
  • Possibly all animals, principally horses
  • Acute
  • Recurrent
  • Chronic
  • Seasonal/non-seasonal
  • May progress to crusting/sloughing
  • Variable pruritus
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12
Q

What are the main triggers for uritcaria and angioedema? 6

A
  • administered/applied substances
  • infections, systemic/focal
  • parasitic infestation, insect bites/stings
  • dietary components
  • aeroallergens
  • contact allergenss
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13
Q

What are less important triggers for urticaria and angioedema?

A
  • other environmental substances
  • systemic disease
  • physical stimuli
  • hereditary conditions
  • autoAbs
  • idiopathic
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14
Q

How can urticaria and angioedema be diagnosed?

A
  • Avoidance and re-challenge

- For IgE-mediated (immediate) allergies –> demonstrate allergen-specific IgE. Mites, insects and pollens only

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15
Q

What type of reaction is a food hypersensitivity? 2

A

FOOD ALLERGY and FOOD INTOLERANCE have IMMUNOLOGICAL components:
ALLERGY - IgE mediated OR non-IgE mediated
INTOLERANCE - idiosyncratic, pharmacological, metabolic

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16
Q

What are the CS of food hypersensitivity?

A

GIT: gastroenteritis, enteropathy
SKIN: urticaria, angioedema, pruritic skin disease, trigger of AD?, possible in dog, cat and horse.

17
Q

Tx - cutaneous adverse food reaction/food hypersensitivity 3

A
  • allergen avoidance
  • treat secondary complications
  • GCs if allergen avoidance is not possible
18
Q

Dx - cutaneous adverse food reaction/ food hypersensitivity

A
  • Hx and Cs
  • response to restricted diet + relapse on old diet
  • (intradermal and serological tests of no benefit)
19
Q

What is CAD

A

Canine Atopic Dermatitis

20
Q

Outline the aetiology of CAD

A

GENETICS - skin barrier, IgE response, (skin) immune system

ENVIRONMENTAL FACTORS - decreased skin barrier, allergen exposure, type of early immune stimulation

21
Q

What is a typical Hx for AD?

A
  • age at onset typically 6m-3 years
  • breed, (WHWT, Shar Pei, Boxer, Retriever, English Setter)
  • Family
  • Pruritus, rash, ear infection
  • Timing - seasonal, non-seasonal, non-seasonal with seasonal exacerbation, intermittent
22
Q

What primary lesions are associated with AD? 3

A

(Pruritis +…)

  • none
  • erythema
  • eryhtematous maculopapular rash
23
Q

What is important to remember about breeds and AD?

A
  • Some breeds affected earlier (French Bull, Shar Pei)

- Accuracy of diagnostic criteria variable

24
Q

What are the 2 main causes of allergic skin disease?

A
  • AD

- Food allergy

25
Q

What are the 2 main causes of skin (ear) infections?

A
  • immunological derangement

- cutaneous abnormalities (skin barrier)

26
Q

What are the 2 main pathogens implicated in ear infections?

A
  • Staphylococcus pseudintermedius

- Malassezia pachydermatis

27
Q

Dx - AD

A
  • Hx
  • CS
  • Rule out/resolve other pruritic Dx (ectoparasites, skin infections)
  • Investigate food hypersensitivity
28
Q

What are criteria need to be met for an AD diagnosis?

A

5 CRITERIA OUT OF THE FOLLOWING TO BE MET:

  • age at onset < 3 years
  • mostly indoor
  • corticosteroid-responsive pruritus
  • chronic/recurrent yeast infections
  • affected front feet
  • affected pinnae
  • non-affected ear margins
  • non-affected dorso-lumbar area
29
Q

When should you use allergy tests in the context of AD?

A

NOT FOR DIAGNOSIS. Use AFTER AD diagnosis has been made.

Use for MANAGEMENT (i.e. avoidance and immunotherapy) therefore has a supportive role.

30
Q

Outline immunotherapy protocol

A

use extract from allergen, inject dog at increasing concentrations to hyposensitise them (i.e. move away from an IgE/Th2 response to a more tolerant response, works in 50% cases)

31
Q

What is the treatment aim for CAD?

A

Reduce pruritus to an acceptable level long-term as safely as possible.

32
Q

How is CAD tx best achieved? 3

A
  • addressing as many trigger factors as possible
  • combine tx modalities
  • custom-tailored tx plan

Dermatology (27 decks)

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