Background: Increased eosinophils in sinus contents are regarded as nonspecific allergic sinusitis. However there are only a few studies addressing the rate of fungal infection associated allergic fungal sinusitis in non-specific allergic sinusitis. This study was to identify the prevalence of allergic fungal sinusitis in the sinus content specimens with increased eosinophils. Methods: A computer search for allergic sinusitis was done over a 4 year period of time. And allergic fungal sinusitis was individually identified within listed allergic sinusitis cases. Each individual case of allergic fungal sinusitis was reviewed in correlation with sinus culture findings and the prevalence of allergic fungal sinusitis was calculated. Results: The rate of allergic fungal sinusitis over allergic sinusitis was 12.8% (in 10 out of 78 cases). Eight patients were female and two were male with age ranging from 18 to 73 years old. Five, one, two and two cases were identified in spring, summer, fall and winter seasons, respectively. Allergic fungal sinusitis showed characteristic mucinous pool with scattered foci of degenerated layers of eosinophils and other inflammatory cells. Silver stained section revealed scattered non-pigmented fungal hyphae in 9 out of 10 cases located in either mucinous pool or degenerated layers of eosinophils. The identity of the fungal hyphae with 45 degree angled branching septa cannot be determined from morphology alone, but two concurrent culture tests from the sinus were positive for Aspergillus fumigatus and the remaining 8 case cultures did not grow fungi. There was no mucosa invasion by the fungi. Conclusion: Our data indicate that the allergic fungal sinusitis represented a small portion of nonspecific allergic sinusitis. Spring appears to be the season with more such cases, which implies that the fungal infection (most likely one of Aspergillus species) can be associated with one of seasonal allergic etiologies.
Zhang PL, Kanaan DH. Prevalence of allergic fungal sinusitis in nonspecific allergic sinusitis. Histopathology. 2022 October; 80(S1):111.