Severe asthma: from phenotypes (clinical features) to endotypes (genetics and biology)

Heterogeneous disease

Asthma, and severe asthma, in particular, is a heterogeneous disease.

Traditional views of asthma have centered around a childhood onset disease with an allergic component. However, severe asthma can present in multiple different ways, and only 30-50% meet traditional childhood onset allergic criteria.



Severe asthma - differential diagnosis and management (click to enlarge the image).

Phenotypes

A phenotype is clinical characteristics that are the product of the interaction of the patient's genes with the environment.
There are 3-5 common clinical phenotypes of severe asthma in adults:

- early onset severe allergic asthma
- late onset non-atopic eosinophilic asthma
- late onset non-eosinophilic asthma with obesity

However, there is a big problem with the phenotypes - they do not identify a target population for a specific therapy.

Endotypes

As biological characteristics are better identified (cell markers, interleukins, etc.), phenotypes could evolve into asthma endotypes.

Endotypes could be identified based on matching:

- genetics
- biology (cell types, interleukins)
- therapeutic responses

This integration of genetics, biology and clinical characteristics can enabled us to effectively treat complex heterogeneous diseases, such as severe asthma.



References:

Current treatment of severe asthma. Hashimoto S, Bel EH. Clin Exp Allergy. 2011 Dec 12. doi: 10.1111/j.1365-2222.2011.03936.x.

Figures:

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