Allergy in the Lungs

Question 1

Define intolerance

Answer 1

It is the inability to cope with normally acceptable conditions/exposure

Question 2

Explain the difference in the immune system between an immediate allergy response and a delayed allergy response

Answer 2

Immediate response - First there is exposure, recognition and then memory. Mediated by IgE and Mast cell interactions, it involves IL-4 and IL-33.
Delayed allergic response - Mediated by reactive T cells and involves IL-12 and Interferon

Question 3

What is allergy?

Answer 3

• Clinical reaction which can be acute or slow and progressive (which may lead to tissue remodelling). It occurs due to an immune system intolerance

Question 3

What is the difference between hyper-reactivity and allergy

Answer 3

Hyper-reactivity - A response which is greater than the average. (scale)
Allergy - Is having a hypersensitivity response to an allergen which other people do not have. (either allergic or non-allergic)

Question 4

What are the effects of allergies in the lungs?

Answer 4

• If it affects the airways then is can affect airflow causing increased resistance which results in a wheeze/stridor due to turbulent flow.
• If it affects the alveola (parenchyma) then it can affect gas transfer

Question 5

What are the clinical consequences for an allergy in the lungs?

Answer 5

• Narrowing of medium to small airways which are not supported by cartilage. this can cause a expiratory phase narrowing (wheeze) or impair muco-ciliary clearance

Question 6

What re the physiological, pathological and clinical definitions of asthma

Answer 6

Physiological - Reversible/variable airflow obstruction.
Pathological - Chronic airway inflammation/allergy.
Clinical - triggers which include cold, exercise, cats, nocturnal/diurnal

Question 7

What are the symptoms of asthma?

Answer 7

• Wheeze, cough, yellow/clear sputum, breathlessness and exercise intolerance.
• Symptoms are episodic, diurnal, variable and can be triggered by exercise, allergies, and chemicals

Question 8

What are the histological changes seen in asthma?

Answer 8

There is inflammation, scabby epithelium with a thickened basement membranes and smooth muscle hypertrophy with mast cell infiltration.

Question 9

How is the diagnosis of asthma made?

Answer 9

• Appropriate clinical history (family history of atopy etc)
• Clinical signs at the times of symptoms
• Appropriate supportive physiological tests (peak flow diary)

Question 10

Explain the management of asthma in adults

Answer 10

1st line - SABA and if this is used more than 3x a week then give inhaled corticosteroid.
Add on therapy (if using SABA more than 3x weekly) - Inhaled LABA (long acting beta 2 agonist) eg, salmeterol.
Extra add on therapy - Consider increased ICS dose or adding LTRA (leukotriene receptor antagonist) such as Montelukast.
- After these additions, if patient is still using their SABA 3x weekly then consider specialist referral where they may give biological therapies. Consider theophylline.

Question 11

What is the immune response to an allergy of the lung parenchyma

Answer 11

• Delayed immune response results in formation of IgG which binds to antigens forming an antibody-antigen complex which causes tissue remodelling. This causes an acute illness, fever and wheeze

Question 12

What are some triggers for hypersensitivity pneumonitis?

Answer 12

• Bird dander,
• Fingal spores,
• Aspergillus,
• Wheat,
• Humidifier lung,
• Mollusca shell

Question 13

What are the symptoms of the acute illness of hypersensitivity pneumonitis

Answer 13

It occurs 4-6 hours after exposure. It is a type III hypersensitivity reaction. It presents with wheeze, cough, fever, chills, headache, myalgia, malaise and fatigue. This may last several days. Diagnosis via bronchoalveolar lavage

Question 14

What are the clinical consequences of the acute illness of hypersensitivity pneumonitis?

Answer 14

It results in thickening of alveolar septae and filling of the alveolus with fluid. This causes hypoxaemia and air space shadowing on a CXR

Question 15

Chronic exposure to the allergen in hypersensitivity pneumonitis can result in what?

Answer 15

• Fibrosis due to interstitial scarring from chronic tissue remodelling. This increases the distance O2 molecules have to travel to reach the blood stream.
• Emphysema due to interstitial destruction from neutrophilic enzyme release. This results in a reduced surface area of the alveoli
• Fibrosis and emphysema cause reduced o2 transport and airspace shadowing on CXR

Question 16

What is the management of hypersensitivity pneumonitis?

Answer 16

• Avoid the allergen
• Consider use of corticosteroids to reduce inflammation
• Potentially may require oxygen supplementation

Question 17

What type of hypersensitivity reaction is hypersensitivity pneumonitis?

Answer 17

Type III.