Eosinophilic Endotype of Asthma.

Asthma is a heterogeneous disease that can be classified into different clinical endotypes, depending on the type of airway inflammation, clinical severity, and response to treatment. This article focuses on the eosinophilic endotype of asthma, which is defined by the central role that eosinophils play in the pathophysiology of the condition. It is characterized by elevated sputum and/or blood eosinophils on at least 2 occasions and by a significant response to treatments that suppress eosinophilia. Histopathologic demonstration of eosinophils in the airways provides the most direct diagnosis of eosinophilic asthma; but it is invasive, thus, impractical in clinical practice.