Allergy and asthma

Question 1

What is intolerance in a clinical setting?

Answer 1

The inability to cope with normally acceptable conditions/exposures

Question 2

What is the difference between allergy and hyper-reactivity?

Answer 2

• hyper reactivity is an increased response to a trigger that causes a response in the normal population
• Allergy is a response to something that does not cause any reaction in the normal population

Question 3

What causes wheeze/stridor in the airways in the lungs?

Answer 3

Increased resistance causes wheeze/stridor due to turbulence

Question 4

What are the 3 components of asthma?

Answer 4

• Airway inflammation (eosinophil)
• Airway hyper-responsiveness
• Airway narrowing/obstruction that is reversible

Question 5

What is the pathogenesis of asthma?

Answer 5

•Inflammatory mediators cause bronchospasm 
•Mediators:
 - IgE antibodies
- IL-4, IL-33 (IL-5 and IL-13 also) 
- Leukotriene B4
- Tissue damaging eosinophil proteins 
- mast cells

Question 6

What is the treatment of asthma?

Answer 6

• Start with a SABA: salbutamol
• Regular preventer: Inhaled corticosteroid e.g. beclamethasone
• Add on LABA: salmeterol
• Add on LTRA: leukotriene receptor antagonist e.g. montelukast
• Specialist therapies: methyxanthines or monoclonal antibodies

Question 7

What is acute severe asthma?

Answer 7

Any one of:
•PEF 33-50%
•Respiratory rate >/25 breaths per minute
•Heart rate >/110 bpm
•Inability to complete a sentence in one breath

Question 8

What investigations should be carried out in suspected asthma?

Answer 8

• Spirometry
• Bronchodilator reversibility
• Peak flow variability
• Bronchial hypersensitivity

Question 9

What spirometry result is suggestive of asthma?

Answer 9

• FEV1/FVC <70%

* This is positive for obstructive disease and is not asthma specific

Question 10

What bronchodilator reversibility result is suggestive of asthma?

Answer 10

• >/15% increase after 5mg of nebuliser salbutamol

•Increase in volume by >/200ml

Question 11

What variability is suggestive of asthma in a peak flow variability test?

Answer 11

> 20%

Question 12

What is the management of acute severe asthma?

Answer 12

• SABA (salbutamol) via nebuliser (oxygen driven)
• Prednisolone 40-50mg
• +/- antibiotic or a muscarinic antagonist if indicated
• If there is no improvement consider IV magnesium sulphate

Question 13

What are the pathological characteristics of asthma?

Answer 13

• Inflammation
• Scabby epithelium
• Thickened basmenet membrane
• Thickened smooth muscle

Question 14

What are the physiological characteristics of asthma

Answer 14

• Yellow mucous (eosinophils)
• Repair pathways
• Non elastic airways
• Increased responsiveness
• Increased sensitivity

Question 15

Describe histology of the airway in a person with asthma

Answer 15

• Smooth muscle hypertrophy

* Mast cells

Question 16

What bronchial hypersensitivity test result is indicative of asthma?

Answer 16

•A drop of >/20% in FEV1 by

Question 17

What cytokines released by dragged epithelial cells are involved in asthma?

Answer 17

• TNF-a
• TGF-B
• VEGF

Question 18

What do anti-IgE therapies target?

Answer 18

•IgE produced by mast cells

Question 19

What do corticosteroids target in asthma?

Answer 19

• Mast cells
• Macrophages
• T helper cells

Question 20

Explain allergic disease in the lung parenchyma

Answer 20

Type 2 immune response
•First exposure resulting in antigen presenting cell presenting antigen to T cell, forming an immune complex
•IL-12 and IFN, reactive T cells form
•On re-exposure, IgG moderates and immune complexes form
•Tissue remodelling occurs as does an immune response (neutrophils, consolidation)

Question 21

What are the clinical consequences of peripheral/parenchymal disease?

Answer 21

• Thickening of the septae, filling of the alveolus with fluid
• Loss of O2 resulting in hypoxia and normocapnia
• Air space shadowing on the Chest x ray

Question 22

What is fibrosis of the lung?

Answer 22

Interstitial scarring from chronic tissue remodelling/repair pathways

Question 23

What is emphysema?

Answer 23

Interstital destruction from neutrophilic enzyme release

Question 24

What are the clinical consequences of fibrosis and emphysema?

Answer 24

• Reduced oxygen transport into the blood stream
• Measured by carbon monoxide gas transfer during full PFTs
• Airspace shadowing on Chest X ray

Question 25

What is extrinsic allergic alveolitis?

Answer 25

• Acute illness due to type III reaction
• Sub acute days to weeks: Type IV T cell mediated reaction
• Chronic disease - fibrosis and emphysema, the final pathway of all chronic inflammatory conditions

Question 26

What is caused by allergy in the airways?

Answer 26

This will affect the airflow
•Increases resistance
•Causes wheeze/stridor

Question 27

What is the effect of allergy in the parenchyma?

Answer 27

•Affects gas transfer and compliance

Question 28

What is the presentation of allergic disease in the lung parenchyma acutely?

Answer 28

• 4-6 hours after exposure
• wheeze, cough, fever, chills, headache, myalgia, malaise, fatigue
• May last several days
• Serum sickness illness

Question 29

What is the management of EAA?

Answer 29

• avoid trigger
• Inflammation: corticosteroids (neutrophils are moderately steroid responsive), cytotoxics
• Oxygen supplementation