Endotypes and phenotypes of chronic rhinosinusitis: A PRACTALL document of the EAACI & AAAAI

Endotypes and phenotypes of chronic rhinosinusitis: A PRACTALL document of the EAACI & AAAAI

Chronic rhinosinusitis (CRS) is a complex disease consisting ofseveral disease variants with different underlyingpathophysiologies. Limited knowledge of the mechanisms of thesedisease subgroups is possibly the greatest obstacle inunderstanding the causes of CRS and improving treatment. It isgenerally agreed that there are clinically relevant CRSphenotypes defined by an observable characteristic or trait, suchas the presence or absence of nasal polyps. Defining the phenotypeof the patient is useful in making therapeutic decisions. However,clinical phenotypes do not provide full insight into all underlyingcellular and molecular pathophysiologic mechanisms of CRS.Recognition of the heterogeneity of CRS has promoted theconcept that CRS consists of multiple groups of biologicalsubtypes, or ‘‘endotypes,’’ which are defined by distinctpathophysiologic mechanisms that might be identified bycorresponding biomarkers. Different CRS endotypes can becharacterized by differences in responsiveness to differenttreatments, including topical intranasal corticosteroids andbiological agents, such as anti–IL-5 and anti-IgE mAb, and can bebased on different biomarkers that are linked to underlyingmechanisms. CRS has been regarded as a single disease entity inclinical and genetic studies in the past, which can explain thefailure to identify consistent genetic and environmentalcorrelations. In addition, better identification of endotypes mightpermit individualization of therapy that can be targeted againstthe pathophysiologic processes of a patient’s endotype, withpotential for more effective treatment and better patientoutcomes.