Endotyping of Nasal Polyposis

Our understanding of nasal polyposis has changed considerably in the past decade. Distinct phenotypes of the disease have become entrenched in clinical guidelines. These include the allergic variant known as central compartment atopic sinus disease (CCAD), adult-onset eosinophilic chronic rhinosinusitis (eCRS), and a non-eosinophilic CRS (non-eCRS) subtype. These phenotypes necessitate distinct treatment strategies, and the underlying molecular pathophysiology of each is key. This underlying mechanism is referred to as the endotype of CRS—the particular inflammatory profile that drives an individual’s disease—and it is a critical factor that directs treatment, establishes prognosis, and helps our profession to share research at a deeper level than clinical phenotype alone. In an era of emerging targeted biologic therapies, a deeper understanding of the signaling and inflammatory pathways in CRS is critical to ensure appropriate patient care. This chapter explores the concept of endotyping, its application to chronic rhinosinusitis with nasal polyposis, and the limitations of our current understanding.