Asthma Overview and Endotypes

Study Notes

Asthma is a chronic airway disease characterized by inflammation, reversible airflow obstruction, airway hyper-responsiveness, and airway remodeling.
Inflammation is the root cause of all asthma aspects.
Asthma is a heterogeneous disease, meaning different types exist, including different endotypes and phenotypes.

Endotypes describe the inflammatory process behind observed patient characteristics.
Five endotypes of asthma have been proposed: allergic eosinophilic, non-allergic eosinophilic, neutrophilic, paucigranulocytic, and mixed granulocytic asthma.

Phenotypes describe the clinical presentation of asthma in different patient groups.
Five asthma phenotypes are proposed, based on clinical characteristics. Data from research exists for these phenotypes.

Symptoms may be discordant
- Early symptom predominant (atopic, normal BMI, high symptom expression)
Symptoms may be concordant
- Early onset, atopic asthma (Symptoms, inflammation, airway dysfunction)
Other notable asthma symptoms include cough, wheezing, chest tightness, and shortness of breath.

Conventional therapy includes reliever and controller medications.
- Reliever medications (short-acting bronchodilators, beta-2 agonists) dilate the airways.
- Controller medications (corticosteroids, long-acting bronchodilators) reduce the underlying inflammation.
Acute Asthma Exacerbation Treatment
- Inhaled bronchodilators: Beta-2 agonists or anticholinergics, possibly Heliox (helium and oxygen mixture), administered through MDI or nebulizer.
- Systemic corticosteroids: Prednisone, prednisolone, or methylprednisolone, sometimes intravenously.
- Subcutaneous epinephrine (1mg/mL, 1:1000 solution or Terbutaline is an alternative for children, but is no longer produced in large quantities and is expensive.
- Antibiotics indicated only when bacterial infection is suspected based on symptoms
- Magnesium sulfate: an airway smooth muscle relaxant, but use is controversial due to lack of confirmed efficacy and safety.