Eosinophilic Mucin Rhinosinusitis: A Distinct Clinicopathological Entity

Abstract

Background Allergic fungal sinusitis (AFS) was recognized in 1981. Since 1983, a form of sinusitis histologically similar to AFS except for the absence of fungal hyphae has also been noted. The designation “eosinophilic mucin rhinosinusitis (EMRS)” is proposed. Its relationship to AFS is controversial and problematic. Objective To determine whether distinctive clinical and immunological differences exist to differentiate the histological entity of EMRS from AFS. Study Design Literature review and comparison of cases of AFS (n = 418) to EMRS (n = 40) from the literature, as well as cases of AFS (n = 13) and EMRS (n = 29) accrued in the present study. Results A total of 431 AFS patients were compared with 69 EMRS patients. The mean age of patients with AFS was significantly younger than patients with EMRS (30.7 y compared with 48.0 y, respectively;P < .001). Male‐to‐female ratios were 1.03:1 and 1.26:1 for AFS and EMRS, respectively, and were not significantly different. Forty‐one percent of patients with AFS were asthmatic compared with 93% of patients with EMRS (P < .0001). Thirteen percent of patients with AFS were aspirin sensitive compared with 54% of patients with EMRS (P < .0001). Polyp occurrence was almost 100% in both groups. Eighty‐four percent of patients with AFS had allergic rhinitis (AR), while only 63% of patients with EMRS had AR (P = .004). Fifty‐five percent of AFS patients had bilateral disease, in contrast to the 100% of EMRS patients with bilateral disease (P < .0001). Although average total immunoglobulin E (IgE) was elevated in both groups, it was significantly more elevated in AFS patients (range, 12–13,084 mg/dL; mean, 1,941 mg/dL) compared with EMRS patients (range, 14–1,162 mg/dL; mean, 267 mg/dL;P < .001). Total immunoglobulin G (IgG) and IgG subclasses were seldom reported in the cases available from the literature of either AFS or EMRS. However, in the present series of EMRS, IgG1 deficiency occurred in 50% of evaluated patients (mean, 475 ± 175 mg/dL; range, 250–869 mg/dL; normal, 422 to 1,200 mg/dL) but in no cases of AFS reported in the literature. Conclusions Significant clinical and immunological differences exist to distinguish AFS from EMRS. It is postulated that AFS is an allergic response to fungi in predisposed individuals, while EMRS occurs because of a systemic dysregulation of immunological controls. Because EMRS is a systemic disease, unilateral disease is not seen. In contrast, AFS, an allergic response to fungi, may occur unilaterally or bilaterally depending on the antigenic stimulation. EMRS also has a significantly higher association with asthma, an increased incidence of aspirin sensitivity, and an increased incidence of IgG1 deficiency. Therapy with a systemic steroid, a potent and indiscriminant anti‐inflammatory agent, is a useful adjunct in both disorders. Fungal immunotherapy following surgical extirpation of AFS is useful in preventing AFS recurrence. It is predicted that fungal immunotherapy and antifungal agents will be ineffective in patients with EMRS. It is important to differentiate these two similar histopathological entities in future trials assessing therapeutic efficacy. Inclusion of both entities in a study could obscure recognition of the true effectiveness of intervention, because of the possible variable response differences between the two entities. This study shows that significant clinical and immunological differences exist between EMRS and AFS. The future awaits an exploration of the pathophysiological basis of these differences.