Asthma is a chronic respiratory condition. There are different types of asthma, also known as phenotypes or endotypes.
Some phenotypes include allergic asthma, late-onset asthma, and exercise-induced asthma.
In this article, we discuss what asthma phenotypes are, provide some examples of the different types, and discuss what this means in terms of understanding this condition.
Although all people with asthma share similar symptoms and potential lung complications, every case is very different and can range from mild to severe.
This development in the understanding of asthma can further ensure people receive the correct treatment for their particular type.
Endotype vs. phenotype
Endotype is another term a person may come across when looking into asthma phenotypes.
Endotype refers to the mechanistic pathway leading to the condition. In other words, it is the biological process that causes the particular phenotype a person has. Conversely, phenotype refers to how asthma presents within an individual.
There are various types of asthma. Below, we provide a breakdown and explain some of the different phenotypes and endotypes:
Some phenotypes of asthma include:
This is a common form of asthma. The American Academy of Allergy Asthma and Immunology (AAAAI) says it may occur in 40–50% of people with the condition.
It occurs as a response to allergies, such as pollen and dust.
As this is a common phenotype, a person with this type of asthma will be most likely to receive a quick and simple diagnosis.
A 2015 study suggests that a person with this phenotype of asthma may not have their disease under control. This is because people get less treatment for it and often do not receive a diagnosis. The authors advise these individuals to seek regular care so they can help properly manage their condition.
Late-onset asthma, or adult-onset asthma, is where a person develops the condition during adulthood.
Females are more likely to develop the condition after the age of 20 years.
There are a variety of possible causes of late-onset asthma, including obesity, allergies, hormonal changes, and illnesses.
A person with this phenotype of asthma will experience flare-ups during or after exercising.
It occurs in 40–90% of people with asthma. This is because if a person with asthma exercises to a certain level, this may be the cause of a flare-up.
Someone with this type of asthma may need to use their inhaler for a short time before exercising to try and avoid these asthma attacks.
Endotypes differ according to the affected cells or molecules. Some examples of endotypes include:
Eosinophilic asthma is often a severe and persistent type of asthma. It usually occurs due to inflammation in the airway, resulting in a buildup of mucus and fluid. It is common in individuals with allergies.
It is most commonly observable in adults who develop asthma later in life. However, sometimes children can develop this type.
The treatment for this endotype is usually with inhaled corticosteroids. More severe cases may be treatable with biologic agents such as dupilumab or mepolizumab.
This is another form of severe and persistent asthma that causes inflammation in the airways. However, research into this endotype is less forthcoming than eosinophilic asthma.
This is commonly observable in adults who have bacteria in their respiratory tract.
However, it does not usually respond well to corticosteroid treatment.
Knowledge of these different phenotypes and endotypes of asthma means that people can get more appropriate treatment for the specific form of the condition they have.
For example, corticosteroid treatment is usually effective for eosinophilic asthma but not for neutrophilic. If doctors know which type a person has, they can treat it accordingly.
However, the different phenotypes may be difficult for a doctor to diagnose. Additionally, someone may exhibit symptoms of more than one asthma phenotype.
The AAAAI states that further research needs to take place into asthma phenotypes.
An asthma phenotype refers to the different types of asthma, ranging from allergic asthma to exercise-induced asthma. If a person receives a diagnosis of a specific phenotype, this can make treatment easier.
However, these phenotypes may be difficult to diagnose. That said, knowledge of the different phenotypes can lead to people receiving more optimized treatments for their condition.