Definition of Asthma
The GINA definition states that asthma is ‘a heterogeneous disease, usually characterised by chronic airway inflammation’. It is defined by ‘the history of respiratory symptoms such as wheeze, shortness of breath, chest tightness and cough that may vary over time and in intensity, together with variable airflow limitation which may later become permanent.’[1] Several asthma phenotypes have
The GINA definition states that asthma is ‘a heterogeneous disease, usually characterised by chronic airway inflammation’. It is defined by ‘the history of respiratory symptoms such as wheeze, shortness of breath, chest tightness and cough that may vary over time and in intensity, together with variable airflow limitation which may later become permanent.’[1]
Several asthma phenotypes have been described and are recognised by their clinical and pathophysiological features. These are important when considering the option of prescribing a biologic agent.
Common phenotypes seen in clinical practice include:
• Allergic (extrinsic) asthma: This is the most common phenotype. Childhood onset is common, with a personal or family history of atopic disorder such as allergic rhinitis, allergic conjunctivitis, eczema, asthma, or food and drug allergy. It is characterised by eosinophilic airway inflammation and generally has a good response to inhaled corticosteroids.
• Non-allergic (intrinsic) asthma: No evidence or history of allergy. May have neutrophilic inflammation with less response to an ICS.
• Late onset/adult-onset asthma: Presents with asthma for the first time in adulthood. Usually non-allergic and may require a higher dose of ICS.
• Asthma with ‘fixed airflow limitation’: Usually long-standing asthma with poor control and failure to normalise lung function owing to airway remodelling despite intensive treatment.
Other sub-phenotypes (which may fit into the above but with special features):
• Exercise-induced asthma (EIA): Exercise-induced symptoms may be the only manifestation of asthma in young patients with allergic asthma. Managed with usual asthma therapies.
• Cough variant asthma: Cough is the major manifestation of asthma and more common in children. Managed with usual asthma therapies.
• Asthma with obesity: Increasingly more common, in line with trends in the global obesity epidemic, with high symptom frequency and less responsive to an ICS.
• Work-related asthma: Asthma caused (occupational asthma) or aggravated (work-aggravated asthma) by exposure to agents in the workplace. A detailed occupational history is essential to suspect occupational asthma. Once diagnosed, removal from exposure is an essential step. While some patients’ asthma may improve following removal from exposure, the asthma may persist despite removal from exposure. Treatment of asthma is according to standard guidelines. Patients with occupational asthma are entitled to compensation under SA labour law and should be referred to centres of expertise in occupational health.[6]
• Catamenial asthma: One-fifth of women with asthma may have premenstrual worsening of symptoms.
• Aspirin-exacerbated respiratory disease: Aspirin may cause exacerbations in those with aspirin sensitivity previously known as aspirin-induced asthma. Patients with suspected aspirin sensitivity should be referred to a specialist.
Guidelines for the management of asthma in adults and adolescents, South African Thoracic Society, 2021