Asthma is a chronic inflammatory disease of the respiratory system characterized by bronchial hyperresponsiveness, episodic acute asthma exacerbations, and reversible airflow obstruction. Allergic (extrinsic) asthma usually develops in childhood and is triggered by allergens such as pollen, dust mites, and certain foods. Nonallergic (environmental or intrinsic) asthma usually develops in patients over the age of forty and can have various triggers, such as cold air, medications (e.g., aspirin), exercise, and viral infections. The cardinal symptoms of asthma are intermittent dyspnea, cough, and high-pitched expiratory wheeze. Symptoms remit in response to antiasthmatic medications or resolve spontaneously upon removal of the trigger. In a patient with , diagnosis is confirmed by demonstrating reversible bronchial obstruction on pulmonary function tests. Additional tests may be required to evaluate for asthma triggers and comorbidities that increase the risk of acute exacerbations. Treatment regimens differ based on the severity of asthma but primarily consist of different combinations of beta-2 agonists and inhaled corticosteroids (ICS). Systemic corticosteroids are usually reserved for patients with severe persistent asthma. To achieve symptomatic control and minimize the risk of exacerbations, comorbidities should be managed and exposure to asthma triggers minimized. Follow-ups are essential to monitor the response to therapy and to adjust treatment regimens in a stepwise manner.
“Exercise-induced bronchoconstriction” are discussed in their own articles.” and “
- Asthma: a chronic inflammatory disease of the respiratory system characterized by bronchial hyperresponsiveness, episodic exacerbation (asthma attacks), and reversible airflow obstruction; manifests with reversible cough, wheezing, and dyspnea
- Acute asthma exacerbation: a reversible worsening of the clinical features of asthma that develops over a short period of time and can progress to life-threatening asthma; may be the first manifestation of asthma in some patients
- Allergic asthma: the most common type of asthma; begins with intermittent symptoms in childhood and is usually associated with atopy (e.g., eczema, rhinitis) and a good response to treatment
- Nonallergic asthma: an uncommon type of asthma that is not related to atopy and is typically associated with a poor response to standard treatment (e.g., ICS)
- See also “Subtypes and variants.”
- 5–10% of the US population
- More common in black than white patients
- For unknown reasons, the prevalence of asthma has been increasing over the past 20 years. 
- Sex: differs depending on age of onset
- Age of onset
Epidemiological data refers to the US, unless otherwise specified.
- The exact etiology of asthma remains unknown.
- Risk factors for asthma include:
- See also .
- Several factors can trigger an initial asthma attack or cause acute asthma exacerbation.
|Allergic asthma |
|Nonallergic asthma |
Childhood exposure to second-hand smoke increases the risk of developing asthma.
Common underlying pathophysiology
Asthma is an inflammatory disease driven by T-helper type 2 cells (Th2-cell) that manifests in individuals with a genetic predisposition. It consists of the following three pathophysiologic processes:
- Bronchial hyperresponsiveness
- Symptoms are primarily caused by inflammation of the terminal bronchioles, which are lined with smooth muscle but lack the cartilage found in larger airways.
- Overexpression of Th2-cells → inhalation of antigen results in production of cytokines (IL-3, IL-4, IL-5, IL-13) → activation of eosinophils and induction of cellular response (B-cell IgE production) → bronchial submucosal edema and smooth muscle contraction → bronchioles collapse 
- Endobronchial obstruction caused by:
- Allergic asthma
- Irritant asthma: irritant enters lung → ↑ release of neutrophils → submucosal edema → airway obstruction
- (NSAID-exacerbated respiratory disease) is characterized by the Samter triad:
- Typical features: The following features are usually intermittent and can occur either sporadically or in response to an .
- Atypical features: See “Subtypes and variants.”
- Features of common comorbid conditions (e.g., atopic conditions like allergic rhinitis, or eczema)
- is covered in detail separately.
Characteristic examination findings may not be present between episodes of asthma exacerbation!
Subtypes and variants
- Adult-onset asthma: an uncommon phenotype in which patients present with symptoms for the first time in adulthood; more likely to be nonallergic and involves a poor response to standard treatment
- Cough variant asthma: : a form of asthma in which the predominant symptom is chronic dry cough, without other characteristic symptoms of asthma, e.g., wheeze, congestion, dyspnea (see also “Cough”)
- Exercise-induced bronchoconstriction: covered separately in its own article
Asthma-COPD overlap is not a distinct disease entity, but a term used to describe a heterogeneous category of patients with features of both diseases. 
Clinical features 
- Chronic presentation, most commonly with intermittent or episodic symptoms
- Common symptoms include cough, SOB, chest tightness, and wheezing.
- Symptoms may:
- Worsen after exposure to common triggers for asthma, e.g., pollen
- Improve after use of antiasthmatic medications
- May develop in patients with a known history of asthma or COPD
- See also “Comparison of asthma and COPD.”
- Take a comprehensive history, including smoking history and toxin exposure.
- All patients require spirometry and and , if not already performed.
- The diagnosis of asthma-COPD overlap can be made when all of the following criteria are met: 
Do not wait for diagnostic confirmation before initiating treatment for asthma in patients with suspected asthma-COPD overlap; untreated patients are at risk of life-threatening acute asthma attacks. 
- Refer to a pulmonologist for any of the following:
- All other patients
- Initiate ICS, even if the diagnosis is not yet confirmed.  with low-dose or medium-dose
- Add LABA and/or LAMA as needed for the treatment of COPD according to the GOLD group classification system.
- Optimize management of both underlying conditions with:
- If no improvement after 2–3 months, refer to a pulmonologist.
General principles 
- Asthma can be diagnosed in patients ≥ 5 years of age, based on a combination of: 
- Consider adjunctive studies as needed:
- To identify common comorbidities
- To exclude
- are covered separately.
Pulmonary function testing 
- Characteristic findings (observable using any of the PFT modalities described below)
|Diagnostic testing in asthma |
|PFT modality||Supportive findings||Test characteristics|
|Peak flow meter (PFM)|
- Allergy workup: Consider if allergens are suspected to play a significant role in exacerbations.
- Evaluation for additional asthma triggers: e.g., see “Rhinitis”, “Sinusitis”, “GERD” 
Additional diagnostic studies (not routinely recommended)
- Sputum analysis revealing one or more of the following:
- normal or ↑ DLCO:
Fractional exhaled nitric oxide (FeNO)
- The concentration of nitric oxide in exhaled air.
- Usually elevated in response to airway inflammation (e.g., allergic/eosinophilic asthma, atopy, eosinophilic bronchitis)
- Although not routinely recommended, FeNO measurement may be useful for distinguishing between inflammatory and noninflammatory asthma and guiding allergic asthma treatment; higher FeNO levels indicate more inflammation and the potential need to escalate therapy.
- May be elevated in allergic asthma 
The main alternate COPD. The main differentiating features are detailed below. See also “ ,” “ ,” “ ”, and “ ” for other conditions that can mimic asthma.to consider is
Comparison of asthma and COPD
|Age at diagnosis|| |
|Etiology|| || |
|Clinical presentation|| || |
|Bronchial obstruction|| || |
Reactive airway disease 
- A nonspecific term used to describe symptoms and findings that are similar to those of asthma (e.g., wheezing, coughing, airway sensitivity)
- Underlying conditions include asthma, pneumonia, COPD, and/or bronchitis
- Most commonly used in pediatric settings when asthma is suspected, but not yet confirmed
- Clinical features: wheezing, coughing, dyspnea, and/or sputum production
Ascription of the label “Reactive airway disease” may prevent a thorough workup of the actual underlying condition and/or lead to the prescription of ineffective medication.
The differential diagnoses listed here are not exhaustive.
General principles 
- Long-term management of asthma involves a combination of treatment, close follow-up, and patient education.
- Goals for managing asthma
- Specific asthma variants and phenotypes (e.g., exercise-induced asthma) require tailored treatment.
- For the management of exacerbations, see “Acute asthma exacerbation.”
The key to long-term asthma management is a continuous cycle of clinical assessment and treatment adjustment.
- Confirm .
- Assess severity (see “ ”).
- Initiate based on severity.
- Manage comorbidities; reduce exposure to asthma triggers (see “Adjunctive therapy”).
- Monitor response to therapy.
- Adjust treatment (step up or step down) based on response to therapy.
- Schedule frequent follow-ups.
Long-term follow-up and reassessment of asthma symptom control are recommended every 1–6 months.
Assessment of severity
The National Asthma Education and Prevention Program (NAEPP) guidelines classify asthma severity as intermittent or persistent in individuals who have not yet been initiated on long-term therapy based on the following: 
- Symptom severity
- Degree of impairment in lung function
- Frequency and risk of exacerbations
- The 2020 Global Initiative for Asthma (GINA) guidelines classify severity into well-controlled, partly-controlled, and uncontrolled based on the minimum level of long-term treatment required to achieve symptom control (not detailed here). 
Classification of asthma severity in adults and children ≥ 12 years of age (NAEPP) 
The most severe category of any feature determines the severity.
|Class||Symptom severity||Lung function||Exacerbations requiring systemic corticosteroids|
|Intermittent asthma|| || |
|Persistent asthma||Mild persistent asthma|| || |
|Moderate persistent asthma|| |
|Severe persistent asthma|| |
- Different combinations of daily and rescue therapies are given in a stepwise fashion until symptoms are controlled. 
- In treatment-naive patients, the initial treatment regimen should be guided by the , clinical judgment, and patient preference.
- Consult asthma specialists for treatment of step 4 and higher; consider specialist consultation for step 3 treatment. 
- The recommendations here are consistent with the 2020 NAEPP guidelines; in areas in which they differ, the 2020 GINA guideline recommendations are also discussed.
- Treatment of patients ≥ 12 years is detailed here; regimens differ according to the patient's age (see “Tips & links” for guidance on management of asthma in infants and children < 12 years of age).
Stepwise pharmacological treatment of chronic asthma in adults and children ≥ 12 years old (NAEPP)
|Treatment steps|| |
Single inhalers are preferred for combination medications.
|Rescue inhaler (as needed)|
| || |
|Preferred|| || |
|Alternatives|| || |
Step 3 (moderate persistent asthma)
|Alternatives|| || |
Step 4 (moderate to severe persistent asthma)
|Alternatives|| || |
Step 5 (severe persistent asthma)
|Preferred|| || |
Step 6 (severe persistent asthma)
| || |
Any change in treatment regimen should be monitored closely with regular follow-ups.
General principles 
- The goal of antiasthmatic pharmacotherapy is to counteract bronchoconstriction by reducing bronchial inflammation and parasympathetic tone.
- Asthma relievers: drugs effective in acute asthma exacerbation: SABAs, SAMAs, and systemic corticosteroids 
- Asthma controllers: drugs effective in the long-term management of asthma (i.e., not for acute management) 
Commonly used medications 
Overview of commonly used asthma medications 
Dosages detailed here are for adults or children ≥ 12 years of age (unless specified)
|Class||Examples||Mechanism and uses||Adverse effects||Contraindications||Interactions|
|Short-acting beta-2 agonists (SABA)|| || |
|Long-acting beta-2 agonists (LABA)|| || |
|Inhaled corticosteroids (ICS) || || || |
|Leukotriene receptor antagonists (LTRAs)|| || || || |
|Long-acting muscarinic antagonists (LAMA)|| || || |
|Short-acting muscarinic antagonists (SAMA)|| |
Inhaled corticosteroids do not take full effect until they have been used for approx. 1 week.
These medications are not commonly used in clinical practice. They are typically reserved for special cases under the guidance of a specialist.
|Overview of additional asthma drugs|
|Agents||Indications||Mechanism of action||Adverse effects||Contraindications||Interactions|
|Leukotriene pathway modifiers (e.g., zileuton) || || || |
|Mast cell stabilizers (chromones; e.g., cromolyn sodium, nedocromil sodium) || || || || || |
|Methylxanthines (e.g., theophylline)|| || || |
|Biologics|| || || |
|IL-5 antibodies (e.g., mepolizumab, reslizumab,benralizumab) || |
Theophylline is no longer routinely prescribed due to the risk of toxicity. It is used solely as an adjunctive or alternative therapy.
- Reducing exposure to triggers or allergens
- Managing comorbidities
- Reducing the risk of infection-induced exacerbations
- Lifestyle recommendations
- Social interventions 
Special patient groups
Asthma in pregnancy
- Asthma symptoms may be worse, better, or unchanged during pregnancy.
- Same stepwise management as with other patients
- Inhalation treatments preferred
- Poorly managed asthma can increase the risk of pregnancy complications (e.g., preeclampsia, premature birth, congenital abnormalities).
- Monthly monitoring of asthma is recommended.
Children under 5 years of age
- Asthma in patients under 5 years of age is challenging to diagnose and is often underdiagnosed, as children in this age group are not typically able to adequately perform the spirometric maneuvers.
- Regimens containing corticosteroids are preferred as initial therapy in infants and young children; see “Tips & links” for details on treatment regimens and dosages. 
- Young children (< 5 years) may require nebulizers because of difficulty using inhalers. 
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