Controversies surrounding the categorization of fungal sinusitis.

Though rhinosinusitis is a common disorder, controversies surround the categorization of chronic rhinosinusitis (CRS) and the role of fungus in CRS. The diagnosis of each category is important for optimum therapy and predicting the course. Based on histopathological findings, fungal rhinosinusitis (FRS) can be broadly divided into two categories: the invasive and non-invasive depending on invasion of the mucosal layer. Three types of FRS are tissue-invasive: acute invasive, chronic invasive, & granulomatous. The two non-invasive FRS disorders are fungal ball, and fungus related eosinophilic rhinosinusitis including allergic fungal rhinosinusitis (AFRS). The distinction of granulomatous from chronic invasive type is not beyond controversy as both types have a chronic course and predominant orbital involvement. Maximum confusion surrounds the entity of fungus-related eosinophilic rhinosinusitis, and the definition of AFRS. In the diagnosis of AFRS, the detection of fungi in allergic mucin is considered important, although hyphae are sparse in sinus content. This leads to confusion in definition of this entity, especially with the description of two more closely related entities--eosinophilic fungal rhinosinusitis (EFRS) and eosinophilic mucin rhinosinusitis (EMRS). Recently reports of histologic invasion in possible cases of AFRS were also documented. Currently, there are more questions than answers concerning the categorization of FRS.