About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Chronic airway inflammation with variable airflow obstruction — diagnosed clinically + spirometry (FEV₁/FVC <0.7 with ≥12% reversibility)
- BTS/SIGN stepwise approach: SABA → low-dose ICS → add LABA → increase ICS → add LTRA/theophylline → oral steroids/biologics
- Acute severe: cannot complete sentences, RR ≥25, HR ≥110, PEF 33–50% predicted
- Life-threatening: SpO₂ <92%, silent chest, PEF <33%, altered consciousness, hypotension
- Acute treatment: nebulised salbutamol + ipratropium, oral prednisolone 40–50 mg, IV magnesium if life-threatening
Overview
Asthma is a chronic inflammatory disease of the airways characterised by bronchial hyperresponsiveness and variable airflow obstruction that is at least partly reversible. It results from a complex interaction between genetic predisposition and environmental triggers including allergens, exercise, cold air, and respiratory infections. The hallmark is episodic symptoms with interval wellness, distinguishing it from COPD where obstruction is progressive and largely irreversible.
Epidemiology
Asthma affects approximately 5.4 million people in the UK — around 1 in 11 children and 1 in 12 adults. The UK has one of the highest prevalence rates globally. Approximately 1,400 deaths per year are attributed to asthma, the majority of which are preventable. Risk factors include atopy (eczema, allergic rhinitis, food allergy), family history, prematurity, maternal smoking, and obesity. Childhood asthma is more common in boys; adult-onset asthma is more common in women.
Clinical Features
Symptoms
Episodic wheeze — typically worse at night and early morning
Dry cough — may be the sole presenting symptom, especially in children
Breathlessness — variable, often triggered by exercise, allergens, cold air
Chest tightness
Inability to complete sentences in one breath
Symptoms worsen with viral infections, exercise, allergens, NSAIDs, beta-blockers
Signs
Expiratory polyphonic wheeze on auscultation
Prolonged expiratory phase
Hyperinflated chest (chronic severe disease)
Silent chest — absent breath sounds indicating critical airflow limitation
Accessory muscle use, tracheal tug, inability to speak
Cyanosis, exhaustion, bradycardia, hypotension
Investigations
First-line
Spirometry with reversibilityObstructive pattern (FEV₁/FVC <0.7) with ≥12% and ≥200 mL improvement in FEV₁ post-bronchodilator
Peak expiratory flow (PEF)Diary over 2–4 weeks showing ≥20% diurnal variability supports diagnosis. Essential in acute exacerbation assessment
Second-line
FeNO (fractional exhaled nitric oxide)≥40 ppb in adults supports eosinophilic airway inflammation and steroid-responsive disease
BloodsFBC (eosinophilia), total IgE (atopy), specific IgE or skin prick tests if allergic triggers suspected
Chest X-rayUsually normal — useful to exclude differentials (pneumothorax, pneumonia, foreign body)
Specialist
Bronchial challenge testingMethacholine or histamine provocation — if spirometry is normal but clinical suspicion is high
CT thoraxNot routine — consider if atypical features or suspected bronchiectasis/ABPA
1
Step 1 — reliever only
- Short-acting beta-agonist (SABA) as required — salbutamol inhaler
- If using SABA ≥3 times/week → step up
2
Step 2 — add preventer
- Low-dose inhaled corticosteroid (ICS) — beclometasone 200–400 mcg/day or equivalent
- Review inhaler technique and adherence before stepping up
3
Step 3 — add-on therapy
- Add long-acting beta-agonist (LABA) — salmeterol or formoterol
- If good response → continue; if partial response → increase ICS to medium dose
- If no response to LABA → stop LABA, increase ICS, consider LTRA (montelukast)
4
Step 4 — persistent poor control
- Medium-dose ICS + LABA
- Add LTRA (montelukast), theophylline, or tiotropium
- Consider referral to specialist
5
Step 5 — specialist therapies
- High-dose ICS
- Oral prednisolone (lowest dose for shortest duration)
- Biologic therapies: omalizumab (anti-IgE), mepolizumab/benralizumab (anti-IL-5) for severe eosinophilic asthma
- Always maintain on minimal effective step — step down when stable for ≥3 months
6
Acute exacerbation
- Nebulised salbutamol 5 mg + ipratropium bromide 500 mcg
- Oral prednisolone 40–50 mg for 5–7 days (no taper needed)
- Oxygen to maintain SpO₂ 94–98%
- If life-threatening: IV magnesium sulphate 1.2–2 g over 20 min
- If near-fatal: ITU/anaesthetic input, consider IV salbutamol or aminophylline
Complications
- Acute severe/life-threatening attack: Respiratory failure requiring ventilation — the most feared complication
- Pneumothorax: Air trapping and alveolar rupture during severe exacerbation
- Fixed airflow obstruction: Airway remodelling from chronic inflammation leading to irreversible obstruction
- Growth impairment: In children on long-term systemic steroids
- Adrenal suppression: With prolonged high-dose ICS or repeated oral steroid courses
- Oral candidiasis and dysphonia: From ICS — mitigate with spacer device and mouth rinsing
UKMLA Exam Tips
- 1BTS/SIGN steps: SABA → ICS → ICS+LABA → medium ICS+LABA+LTRA → specialist. Know this cold
- 2Silent chest = life-threatening, NOT "improving" — this is the classic exam trap
- 3FeNO ≥40 ppb supports eosinophilic inflammation and predicts good ICS response
- 4Beta-blockers (including eye drops like timolol) are contraindicated in asthma
- 5Acute asthma: give prednisolone 40–50 mg for 5–7 days — you do NOT need to taper short courses
- 6MART regime (Maintenance And Reliever Therapy) uses ICS/formoterol as both maintenance and reliever
- 7If asked about a patient whose asthma worsened after starting an NSAID → aspirin-exacerbated respiratory disease (Samter triad: asthma + nasal polyps + NSAID sensitivity)
practicetest your knowledge on asthmaApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — respiratory and beyond.
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