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Define Asthma

Asthma Aetiology

Asthma Pathogenesis

Macro and Microscopic Features

Define Asthma

Asthma is a chronic inflammatory disorder of the airways that causes recurrent and episodes of wheezing, breathlessness, chest tightness and cough – particularly at night/early morning.

These symptoms are generally associated with widespread bronchoconstriction and airflow limitation (obstruction) that is at least partly reversible by bronchodilators

It is thought that the associated inflammation results in an increase in airway responsiveness (bronchospasm).

Aetiology of Asthma:

Asthma is generally classified as Atopic or Non-Atopic

Atopic Asthma occurs due to Type I Hypersensitivity reaction induced by exposure to antigen. Often associated with a family or personal history of atopy.

Non-atopic Asthma does not occur due to an allergic reaction. It can be triggered by exercise, ingestion of aspirin, pollutants, etc.


In allergic asthma, there are three stages: Sensitisation, Immediate Reaction, and Late Phase Inflammation

In sensitisation, the inhaled antigen sets off a Th2 cell reaction, which results in the production of IgE antibodies. The IgE antibodies coat mast cells and basophils.

Upon re-exposure, exposure to the antigen results in Ige-antigen cross-linking. This results in the release of pre-formed mediators from mast cells: histamine, bradykinin, leukotrienes, prostacyclin, other cytokines. Histamine and other mediators result in brconhoconstriction – the basis of an acute exacerbation.

The later inflammatory phase is caused by an inflammatory response, which occurs later in response to the mediators released earlier. Inflammatory mediators cause increased leukocyte adhesion, increased vascular permeability, etc. The late phase inflammation contributes to the airway remodelling which is characteristic of asthma – airway thickening and increased mucous production.
• Oedematous bronchial walls
• With inflammatory infiltrate
• Hyperplasia of smooth muscle
• Hyperplasia of mucous glands/goblet cells
• Increased mucous production
• Mucous plugging of the airways

Asthma: Macro

Hyperinflated lungs
Prominent bronchi
Plugged with mucous
Thickened bronchial walls

Asthma micro:

Mucous contains whorls of shed epithelial cells – Curshmann spirals
Airway Remodelling: thickened basement membrane, hyperplasia of smooth muscle and glands, immune cell infiltrate and odema in walls, lots of eosinophils





Clinical Presentation


Characterised by the permanent dilation of bronchi and bronchioles caused by destruction of the muscle and elastic tissue, de to (and in association with) chronic necrotizing infections


Caused by: underlying pulmonary infections that are not well treated and progress to chronic necrotizing infections

Hereditary conditions: Cystic fibrosis, Immunodeficiency states, etc.

Post-infectious conditions: e.g. Necrotising pneumonia

Bronchial Obstruction: e.g. due to tumour growth or mucous impaction

Other systemic inflammatory conditions, including rheumatoid arthritis, etc.

Clinical Manifestations:

Cough, fever, expectoration of copious amounts of purulent, foul-smelling sputum


Classification of Restrictive Lung disease:

Restrictive lung disease can be classified according to the type of lesion, and the cause:

Fibrosing: Idiopathic and Identified Cause:

• Non-specific Idiopathic Pneumonia
• Cryptogenic Organising Pneumonia

Identified Cause:
• Association with Collagen Vascular Disease
• Pneumoconioses (induced by organic and inorganic particles)
• Drug Reactions
• Radiation Pneumonitis

• Sarcoidosis
• Hypersensitivity Pneumonitis

• Pulmonary Eosinophilia

Smoking Related:
• Desquamative Interstitial Pneumonia
• Respiratory Bronchiolitis-associated interstitial lung disease
Pulmonary Alveolar Proteinosis