11. Epidemiology, sign, symptoms, pathomechanism, phenotypes and diagnosis of asthma

Question 1

Definition of Asthma

Answer 1

It is a chronic inflammatory condition that causes bronchial narrowing and airflow obstruction, leading to recurrent episodes of wheezing, breahtlessness, chest tightness, and coughing

The airflow obstruction is reversible and not permanent

Question 2

Epidemiology

Answer 2

• In both Europe and USA, prevalence is 5-10%
• One of the **most common childhood chronic diseases **
• Allergic variant usually appears in childhood and can last well into adulthood
• Non-allergic variant typically appears in adults > 40 years old
• Prevalence has been increasing in the last 20 years with no apparent cause
• Asthma prevalence mirrors obesity rates, now obesity is considered a modifiable risk factor for asthma

Question 3

Etiology of Asthma

Answer 3

• Immunological [type 1 HS]
• Genetic [family history]
• Recurrent respiratory infections
• Psychological factors [in about 40% of patients]
• Neurohormonal [increased Vagal tone or decreased Sympathetic tone, ex. at night]

Question 4

Signs and Symptoms of Asthma

Answer 4

• Mild asthma is often asymptomatic between exacerbations
• Severe asthma disease has frequent and harsh exacerbations
• Dysnpea
• Chest tightness
• Wheezing and gasping of air
• Tachycardia and Tachypnea
• Increased work for breathing [accessory muscle involvement]
• Pulsus paradoxus [fall of systolic pressure > 10 mmHg during inspiration]
• Altered consciousness
• Cyanosis
• O2 saturation < 90%

Bolded conditions in severe exacerbation of asthma

In untreated long standing asthma, patients may develop barrel chest. Chest x-ray may show hyperinflation

Question 5

Pathomechanism of Asthma

Answer 5

It is a process driven by Th2 cells causing bronchial hyperresponsiveness, inflammation and endobronchial obstruction

In Allergic type, IgE mediated type 1 HS leads to histamine release from mast cells, causing bronchioconstriction, submucosal edema formation and increased mucus formation.

In Non-allergic type, inhalation of irritant causes release of neutrophils, edema and airway obstruction similar to allergic type

Aspirin exacerbation is characterised by Samter Triad. Chronic rhinosinusitis with nasal polyposis, asthma symptoms

Question 6

Phenotypes of Asthma

Answer 6

• Allergic asthma
• Non-allergic asthma [viral URTI, cold air, GERD]
• Adult-onset asthma
• Occupational asthma
• Cough variant asthma [chronic dry cough without other typical asthma symptoms]
• Aspirin exacerbation respiratory disease
• Asthma-COPD overlap

Asthma-COPD is not an official diagnosis but they can coexist

Question 7

Dx of Asthma

Answer 7

• Detailed patient history
• Physical examination [wheezing on auscultation]
• Spirometry [shows obstruction signs but does improve after bronchial reversibility test; excessive variability on FEV1 and PEF values]
• Peak flow meter when spirometry not available [assess of expiratory flow limitation]
• Bronchial challenge test when spirometry and symptom presentation is inconclusive [to rule out other obstructive causes]