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Year 3 > Allergic disorder (RESP) > Flashcards

Allergic disorder (RESP) Flashcards

1
Q

Define allergic disorder.

A

Conditions caused by hypersensitivity of the immune system to typically harmless substances

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2
Q

Describe the pathophysiology of allergic disorder.

A

IgE binds to receptor on mast cell or basophil, causing degranulation and release of histamine

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3
Q

What are some causes/triggers of allergic disorder? (10)

A
  • dust (mites)
  • foods
  • latex
  • medications
  • insect stings
  • mold spores
  • pet dander
  • pollen
  • genetics
  • stress
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4
Q

What is type I hypersensitivity (allergic disorder)?

A

Antigen reacts with IgE bound to mast cells –> allergic reaction

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5
Q

What conditions can type I hypersensitivity cause (allergic disorder)?

A
  • anaphylaxis
  • atopy e.g. asthma, eczema, allergic rhinitis
  • (triggers: drugs, penicillin, bee/wasp stings, peanuts)
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6
Q

What is type II hypersensitivity (allergic disorder)?

A

Antibody mediated: IgG or IgM binds to antigen on cell surface

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7
Q

What conditions can type II hypersensitivity cause (allergic disorder)? (9)

A
  • autoimmune haemolytic anaemia
  • acute haemolytic transfusion reactions
  • haemolytic disease of newborns (mismatched RhD alleles)
  • immune thrombocytopenia (platelet surface proteins)
  • Goodpasture’s syndrome
  • Graves disease (TSH antibodies bind to thyrotropin receptor)
  • rheumatic fever
  • pernicious anaemia
  • pemphigus vulgaris/bullous pemphigoid
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8
Q

What is type III hypersensitivity (allergic disorder)?

A

Free antigen and antibody (IgG, IgA) combine –> immune complex

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9
Q

What conditions can type III hypersensitivity cause (allergic disorder)? (8)

A
  • serum sickness
  • SLE
  • post-Streptococcal glomerulonephritis
  • vasculitis
  • arthritis (e.g. RA)
  • extrinsic allergic alveolitis (especially acute phase)
  • hepatitis
  • MS
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10
Q

What is type IV hypersensitivity (allergic disorder)?

A

T-cell mediated - sensitised Th cells –> delayed reaction

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11
Q

What conditions can type IV hypersensitivity cause (allergic disorder)? (7)

A
  • TB
  • GvHD
  • allergic contact dermatitis
  • scabies
  • extrinsic allergic alveolitis
  • MS
  • Guillain-Barre syndrome
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12
Q

What can trigger type IV hypersensitivity (allergic disorder)?

A

Nickel salts and hair dyes

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13
Q

What are the clinical features of allergic disorder? (4)

A
  • runny nose & sneezing
  • redness & itching of eyes
  • coughing & wheezing
  • rashes & hives (urticaria)
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14
Q

What investigations are done for allergic disorder? (4)

A
  • skin prick testing - most commonly used, easy to perform and inexpensive - done for type I hypersensitivity reactions (IgE-mediated) that cause systemic reaction
  • scratch testing - done for contact dermatitis and for skin reactions (type IV hypersensitivity, not IgE-mediated)
  • bloods - measure concentrations of specific IgE antibodies
  • serum tryptase - specific marker of mast cell activation
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15
Q

Describe the management plan for allergic disorder. (4)

A
  • antihistamines e.g. cetirizine
  • glucocorticoids
  • emergency - adrenaline auto-injectors for self-treatment (epi-pen)
  • allergen immunotherapy
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16
Q

What are some specific examples of allergic disorder? (3)

A
  • hypersensitivity pneumonitis
  • allergic bronchopulmonary aspergillosis
  • allergic rhinitis
17
Q

Describe the aetiology of hypersensitivity pneumonitis (allergic disorder). (3)

A
  • type III hypersensitivity –> immune-complex mediated
  • type IV also plays a role
  • causes inflammation of alveoli and distal bronchioles
18
Q

What are the causes of hypersensitivity pneumonitis (allergic disorder)? (5)

A
  • bird fancier’s lung: avian proteins from bird droppings
  • farmer’s lung: spores of Saccharopolyspora rectivirgula from wet hay
  • malt worker’s lung: Aspergillus clavatus
  • mushroom worker’s lung: thermophilic actinomycetes
  • occupation exposure to organic dust (including Actinomycetes bacteria, animal proteins or reactive chemicals)
19
Q

How does hypersensitivity pneumonitis (allergic disorder) present? (2)

A
  • acute: 4-8h after exposure, dyspnoea, cough, fever
  • chronic: weeks-months after exposure, dyspnoea, lethargy, productive cough, anorexia, weight loss, bibasilar rales
20
Q

What investigations are done for hypersensitivity pneumonitis (allergic disorder)? (7)

A
  • serologic assays for specific IgG antibodies
  • FBC: no eosinophilia, leukocytosis, anaemia
  • ESR: high
  • albumin: low
  • CXR/CT: upper/mid-zone fibrosis, centrilobular ground glass nodules
  • diffusing lung capacity of CO: decreased
  • bronchoalveolar lavage: lymphocytosis
21
Q

How do we manage hypersensitivity pneumonitis (allergic disorder)? (2)

A
  • avoid precipitating factors
  • oral glucocorticoids (prednisolone)
22
Q

What is the aetiology of allergic bronchopulmonary aspergillosis (allergic disorder)?

A
  • colonisation of airways by Aspergillus fumigatus –> IgE and IgG-mediated immune responses
  • usually in asthmatic and CF patients
  • release of proteolytic enzymes, mycotoxins, antibodies –> airway damage:
    • initially causes bronchoconstriction
    • persistent inflammation –> permanent damage –> bronchiectasis
23
Q

How does allergic bronchopulmonary aspergillosis (allergic disorder) present? (3)

A
  • difficult to control asthma
  • recurrent episodes of pneumonia with wheeze, cough, sputum, dyspnoea, fever, malaise
  • bronchiectasis
24
Q

What investigations are done for allergic bronchopulmonary aspergillosis (allergic disorder)?

A
  • immediate skin test reactivity to Aspergillus antigens
  • Aspergillus-specific IgE radioallergosorbent test - RAST
  • bloods: eosinophilia, raised total serum IgE, raised specific IgE and IgG to A. fumigatus
  • Aspergillus in sputum
  • CXR
  • CT - lung infiltrates, central bronchiectasis
  • PFTs - reversible airflow limitation, reduced lung volumes/gas transfer
25
Q

What does CXR show in allergic bronchopulmonary aspergillosis (allergic disorder)? (4+2)

A
  • transient patchy shadows
  • segmental collapse or consolidation
  • distended mucous-filled bronchi
  • signs of complications:
    • fibrosis in upper lobes
    • bronchiectasis
26
Q

How do we manage allergic bronchopulmonary aspergillosis (allergic disorder)? (2)

A
  • oral corticosteroids (acute)
  • azole antifungal (itraconazole)
27
Q

Describe the aetiology of allergic rhinitis (allergic disorder).

A
  • common URT condition
  • characterised by: nasal pruritus, sneezing, rhinorrhoea, nasal congestion
  • associated symptoms:
    • palate, throat, ear and eye itching
    • eye redness, puffiness, water discharge
  • mediated by IgE-associated response to ubiquitous indoor and/or outdoor environmental allergens
  • sometimes due to occupational/hobby exposures to proteins that do not commonly provoke IgE-mediated responses
  • e.g. woodworkers becoming sensitised to wood dusts, or food service workers becoming sensitised to grain dusts
28
Q

How does allergic rhinitis (allergic disorder) present? (7)

A
  • nasal pruritus
  • sneezing
  • rhinorrhoea
  • nasal congestion
  • palate, throat, ear and eye itching
  • eye redness, puffiness and watery discharge
  • fatigue and irritability
29
Q

What are some risk factors for allergic rhinitis (allergic disorder)? (4)

A
  • Fx of atopy
  • age <20
  • Western lifestyle
  • inadequate exposure to animals and other microorganism-rich environments in early life
30
Q

What investigations are done for allergic rhinitis (allergic disorder)? (4)

A
  • trial of antihistamine or intranasal corticosteroids
  • Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) and Rhinitis Control Assessment Test (RCAT)
  • allergen skin-prick testing
  • in-vitro specific IgE determination
31
Q

How do we manage allergic rhinitis (allergic disorder)? (6)

A
  • oral/intranasal antihistamine (cetirizine) + allergen avoidance
  • oral/intranasal decongestant (oxymetazoline)
  • nasal saline *irrigation**
  • sublingual immunotherapy (SLIT)/subcutaneous immunotherapy (SCIT)
  • LTRA
  • intranasal iprotropium

Year 3 (203 decks)

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