MUC5AC and chronic rhinosinusitis: The criteria for diagnosis of AFRS have undergone numerous revisions; however, most authors agree on the following: the presence in patients with chronic rhinosinusitis (confirmed by CT scan) of characteristic “allergic” mucin containing clusters of eosinophils and their byproducts and the presence of noninvasive fungal elements within that mucin, detectable on staining or culture [2–4, 12].