Endotype

Abstract: Background Current phenotyping of chronic rhinosinusitis (CRS) into chronic rhinosinusitis with nasal polyps (CRSwNP) and chronic rhinosinusitis without nasal polyps (CRSsNP) might not adequately reflect the pathophysiologic diversity within patients with CRS. Objective We sought to identify inflammatory endotypes of CRS. Therefore we aimed to cluster patients with CRS based solely on immune markers in a phenotype-free approach. Secondarily, we aimed to match clusters to phenotypes. Methods In this multicenter case-control study patients with CRS and control subjects underwent surgery, and tissue was analyzed for IL-5, IFN-γ, IL-17A, TNF-α, IL-22, IL-1β, IL-6, IL-8, eosinophilic cationic protein, myeloperoxidase, TGF-β1, IgE, Staphylococcus aureus enterotoxin–specific IgE, and albumin. We used partition-based clustering. Results Clustering of 173 cases resulted in 10 clusters, of which 4 clusters with low or undetectable IL-5, eosinophilic cationic protein, IgE, and albumin concentrations, and 6 clusters with high concentrations of those markers. The group of IL-5–negative clusters, 3 clusters clinically resembled a predominant chronic rhinosinusitis without nasal polyps (CRSsNP) phenotype without increased asthma prevalence, and 1 cluster had a T H 17 profile and had mixed CRSsNP/CRSwNP. The IL-5–positive clusters were divided into a group with moderate IL-5 concentrations, a mixed CRSsNP/CRSwNP and increased asthma phenotype, and a group with high IL-5 levels, an almost exclusive nasal polyp phenotype with strongly increased asthma prevalence. In the latter group, 2 clusters demonstrated the highest concentrations of IgE and asthma prevalence, with all samples expressing Staphylococcus aureus enterotoxin–specific IgE. Conclusion Distinct CRS clusters with diverse inflammatory mechanisms largely correlated with phenotypes and further differentiated them and provided a more accurate description of the inflammatory mechanisms involved than phenotype information only.

Abstract: Chronic rhinosinusitis (CRS) is a complex disease consisting of several disease variants with different underlying pathophysiologies. Limited knowledge of the mechanisms of these disease subgroups is possibly the greatest obstacle in understanding the causes of CRS and improving treatment. It is generally agreed that there are clinically relevant CRS phenotypes defined by an observable characteristic or trait, such as the presence or absence of nasal polyps. Defining the phenotype of the patient is useful in making therapeutic decisions. However, clinical phenotypes do not provide full insight into all underlying cellular and molecular pathophysiologic mechanisms of CRS. Recognition of the heterogeneity of CRS has promoted the concept that CRS consists of multiple groups of biological subtypes, or "endotypes," which are defined by distinct pathophysiologic mechanisms that might be identified by corresponding biomarkers. Different CRS endotypes can be characterized by differences in responsiveness to different treatments, including topical intranasal corticosteroids and biological agents, such as anti-IL-5 and anti-IgE mAb, and can be based on different biomarkers that are linked to underlying mechanisms. CRS has been regarded as a single disease entity in clinical and genetic studies in the past, which can explain the failure to identify consistent genetic and environmental correlations. In addition, better identification of endotypes might permit individualization of therapy that can be targeted against the pathophysiologic processes of a patient's endotype, with potential for more effective treatment and better patient outcomes.

Abstract: Asthma phenotypes have been developed to address the complexities of the disease. However, owing to a lack of longitudinal studies, little is known about the onset as well as the stability of phenotypes. Distinguishing phenotypes with regard to the severity or duration of the disease is essential. A phenotype covers the clinically relevant properties of the disease, but does not show the direct relationship to disease etiology and pathophysiology. Different pathogenetic mechanisms might cause similar asthma symptoms and might be operant in a certain phenotype. These putative mechanisms are addressed by the term ‘endotype’. Classification of asthma based on endotypes provides advantages for epidemiological, genetic, and drug-related studies. A successful definition of endotypes should link key pathogenic mechanisms with the asthma phenotype. Thus, the identification of corresponding molecular biomarkers for individual pathogenic mechanism underlying phenotypes or subgroups within a phenotype is important. Whether newly defined asthma endotypes predict the individual course of asthma has to be validated in longitudinal studies. The accurate endotyping reflects natural history of asthma and should help to predict treatment response. Thus, understanding asthma endotypes might be useful in clinical practice.