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Asthma
Affecting around 10% of children and many adults in the UK, asthma results from complex interactions between genetic susceptibility and environmental triggers. Whilst most people achieve good control with inhaled medications, severity varies widely from mild occasional symptoms to life-limiting disease.
Overview
Asthma is characterised by reversible airway narrowing caused by inflammation, muscle spasm and mucus production in the bronchial tubes. The condition typically begins in childhood but can develop at any age, with symptoms ranging from mild intermittent wheeze to severe daily breathlessness requiring regular medication. Environmental triggers such as allergens, respiratory infections, cold air, exercise and smoke commonly provoke symptom flare-ups in susceptible individuals.
The condition has a substantial genetic component, with children having one affected parent facing approximately 25% risk of developing asthma themselves, rising to around 50% when both parents are affected [PMID:17943260]. However, inheritance follows a complex polygenic pattern rather than a simple Mendelian model, meaning multiple genetic variants each contribute small effects that interact with environmental exposures to determine overall risk. This complexity explains why asthma runs in families but does not follow predictable inheritance patterns seen in single-gene conditions.
Symptoms & clinical features
The cardinal features of asthma include episodic wheezing, shortness of breath, chest tightness and coughing, often worse at night or in the early morning. Symptoms typically vary over time and in intensity, with some people experiencing long symptom-free periods between exacerbations whilst others have persistent daily symptoms requiring ongoing treatment. Coughing may be the predominant feature in some individuals, particularly children, making diagnosis less straightforward.
Triggers vary between individuals but commonly include viral respiratory infections, exposure to allergens such as house dust mite or pollen, exercise, cold air, tobacco smoke, and emotional stress. Symptom patterns often help distinguish asthma from other respiratory conditions: the reversibility of airway narrowing with bronchodilator medication and the variability in symptom severity over hours or days are characteristic features that aid clinical diagnosis.
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Affected organs
Asthma primarily affects the lower respiratory tract, specifically the bronchi and bronchioles-the branching airways that carry air into the lungs. In affected individuals, these airways become inflamed, with thickened airway walls, increased mucus production and heightened sensitivity to triggers. The surrounding smooth muscle can contract excessively in response to triggers, further narrowing the airway lumen and restricting airflow.
Whilst asthma is fundamentally a respiratory condition, severe uncontrolled disease can affect overall quality of life, sleep, physical activity levels and psychological wellbeing. Chronic inflammation in the airways may lead to structural changes over time in some individuals, including airway wall remodelling, though this progression is not inevitable with appropriate management.
Risks & severity
Severity varies considerably between individuals. Many people with asthma experience only mild intermittent symptoms requiring occasional reliever medication, whilst others have moderate persistent asthma needing daily preventer treatment, and a smaller proportion have severe asthma that remains difficult to control despite high-intensity therapy. Risk factors for developing asthma include family history, other atopic conditions such as eczema or hay fever, exposure to tobacco smoke, prematurity, and certain respiratory infections in early childhood [PMID:29716772].
Acute exacerbations can occasionally become life-threatening, particularly if warning signs are not recognised promptly or treatment is delayed. Around 1,200 people die from asthma attacks in the UK annually, many of these deaths considered preventable with optimal management and early intervention during deterioration. Long-term prognosis is generally good with appropriate treatment, and many children with mild asthma experience improvement or resolution of symptoms during adolescence, though asthma can return in adulthood.
Genetic causes
Asthma susceptibility involves multiple genetic variants across numerous genes, each contributing modest individual effects that combine to influence overall risk. Several genes implicated in asthma pathogenesis encode proteins involved in immune signalling and airway inflammation. IL33 encodes interleukin-33, a signalling molecule that promotes type-2 inflammatory responses in airways. Genetic variation in this region has been associated with increased asthma susceptibility in multiple populations [PMID:24390342].
IL4R encodes the interleukin-4 receptor, a cell-surface protein that binds immune signalling molecules involved in allergic inflammation and immunoglobulin E production-pathways central to allergic asthma. Variants affecting IL4R function can influence the magnitude of allergic responses in airways. ORMDL3 encodes a protein involved in sphingolipid metabolism and endoplasmic reticulum stress responses, with variants in this chromosomal region showing robust association with childhood-onset asthma across diverse populations [PMID:17611496]. TSLP encodes thymic stromal lymphopoietin, an epithelial-derived cytokine that initiates allergic inflammatory cascades.
These genetic influences interact with environmental exposures in complex ways, meaning that individuals carrying risk variants may never develop asthma without appropriate environmental triggers, whilst others with lower genetic susceptibility may develop the condition following sufficient environmental provocation.
Inheritance pattern
Asthma does not follow a simple inheritance pattern seen in single-gene conditions. Instead, susceptibility is polygenic-determined by the combined effects of variants in multiple genes, each contributing small increases or decreases in risk. This explains why asthma tends to cluster in families but does not affect relatives in predictable ratios. A child of one affected parent has elevated risk compared to the general population, but the majority will not develop asthma.
Because asthma risk depends on the complex interplay between multiple genetic variants and environmental factors, genetic testing does not currently have a role in predicting individual risk or guiding clinical management. Family history remains a useful clinical risk indicator, but environmental modification and symptom monitoring are more relevant to prevention and early detection than genetic information.
Diagnosis & testing
Asthma diagnosis in the UK typically relies on characteristic symptom patterns combined with objective evidence of variable airflow obstruction. In adults and older children, spirometry showing reversible airway obstruction-improvement in lung function following bronchodilator administration-supports the diagnosis. Peak expiratory flow monitoring demonstrating variability over days or weeks can provide additional evidence. In younger children where spirometry is impractical, diagnosis often rests on clinical assessment of symptom patterns and treatment response.
Diagnosis is usually made in primary care or by respiratory specialists, with most patients managed entirely within NHS primary care. Referral to secondary care respiratory services is appropriate for diagnostic uncertainty, suspected severe asthma, poor symptom control despite treatment, or frequent exacerbations. Genetic testing does not form part of routine asthma diagnosis, as no single-gene test can predict asthma risk or severity given the polygenic nature of susceptibility.
Management & lifestyle
Asthma management in the UK follows stepped approaches outlined in British Thoracic Society and NICE guidelines, aiming for complete symptom control and prevention of exacerbations with minimal medication. Most people achieve good control using inhaled corticosteroids as preventer therapy alongside short-acting beta-agonist relievers for symptom relief. Treatment is stepped up or down according to symptom control, with additional therapies including long-acting bronchodilators, leukotriene receptor antagonists and, in severe cases, biologic therapies targeting specific inflammatory pathways.
Non-pharmacological management includes identifying and avoiding individual triggers where feasible, annual influenza vaccination, smoking cessation support, and maintaining physical fitness. Written personalised asthma action plans help individuals recognise deteriorating control and respond appropriately with treatment intensification. Regular primary care reviews assess symptom control, inhaler technique and adherence. Most people with asthma lead unrestricted lives with appropriate management, though individuals should be aware of deterioration warning signs and seek prompt medical attention during exacerbations.
UK care pathway
The majority of asthma care in the UK is delivered within NHS primary care, with GPs initiating diagnosis, prescribing treatment and conducting regular reviews. Practice nurses often provide asthma education, inhaler technique training and annual assessments. Referral to secondary care respiratory specialists is indicated for diagnostic uncertainty, inadequate control despite optimised primary care management, suspected occupational asthma, or consideration of biologic therapies in severe disease.
Asthma does not typically involve clinical genetics services or genetic counselling, as inheritance is complex rather than following Mendelian patterns, and genetic testing has no established clinical utility for diagnosis or management. Support is available through Asthma + Lung UK (formerly Asthma UK), which provides evidence-based information and a helpline staffed by respiratory nurse specialists.
Frequently asked questions
Is asthma inherited from parents?
Asthma has a genetic component, but inheritance is complex rather than following a simple pattern. Having one parent with asthma increases a child's risk to approximately 25%, rising to around 50% if both parents are affected. However, many people with affected relatives never develop asthma, and many with asthma have no family history, as environmental factors also play crucial roles.
Can genetic testing predict whether my child will develop asthma?
No, genetic testing cannot reliably predict asthma risk because susceptibility depends on variants in multiple genes interacting with environmental factors. Current genetic tests lack the predictive power needed for clinical use. Family history provides some indication of elevated risk, but environmental modification and symptom monitoring remain more useful than genetic information.
Will my asthma get worse over time?
Not necessarily. Many people maintain stable, well-controlled asthma for decades with appropriate treatment. Some children experience improvement during adolescence. However, uncontrolled inflammation can occasionally lead to airway remodelling in some individuals. Optimal management with preventer medications, trigger avoidance and regular monitoring helps preserve lung function long-term.
Should I avoid having children if I have asthma?
Having asthma is not a reason to avoid having children. Whilst your children will have elevated risk of developing asthma compared to the general population, the majority of children with one affected parent do not develop the condition. Asthma in parents does not typically worsen pregnancy outcomes when well controlled, and most people with asthma lead full, active lives with appropriate management.
References
- Gans MD, Gavrilova T. Understanding the immunology of asthma: Pathophysiology, biomarkers, and treatments for asthma endotypes. Paediatric respiratory reviews. 2020. PMID: 31678040
- Boonpiyathad T, Sözener ZC, Satitsuksanoa P. Immunologic mechanisms in asthma. Seminars in immunology. 2019. PMID: 31703832
- Mahesh S, Ramamurthy MB. Management of Acute Asthma in Children. Indian journal of pediatrics. 2022. PMID: 35147928
- Haktanir Abul M, Phipatanakul W. Severe asthma in children: Evaluation and management. Allergology international : official journal of the Japanese Society of Allergology. 2019. PMID: 30648539
- Shipp CL, Gergen PJ, Gern JE. Asthma Management in Children. The journal of allergy and clinical immunology. In practice. 2023. PMID: 36334702
- Schatz M, Rosenwasser L. The allergic asthma phenotype. The journal of allergy and clinical immunology. In practice. 2014. PMID: 25439351
- Akar-Ghibril N, Casale T, Custovic A. Allergic Endotypes and Phenotypes of Asthma. The journal of allergy and clinical immunology. In practice. 2020. PMID: 32037107
- Conrad LA, Cabana MD, Rastogi D. Defining pediatric asthma: phenotypes to endotypes and beyond. Pediatric research. 2021. PMID: 33173175