To calculate the prevalence of asymptomatic localized paranasal sinus aspergillosis (or fungus ball) in the general population and to compare asymptomatic and symptomatic fungus balls (FB) in order to determine their specificities.

Retrospective study including 59 patients operated for FB between 2006 and 2011 in a single unit. Patients were divided into two groups: asymptomatic patients (group 1, n=10), and symptomatic patients (group 2, n=49). All patients in group 1 were identified by systematic screening for a site of infection prior to cataract surgery during this period (n=6198). All patients were treated by endonasal surgery. Calculation of the prevalence of asymptomatic FB was based on standardization of the source population (normal distribution, 95% confidence interval). The two groups were then compared (clinical context, age, history of root canal treatment, topography, recurrence rate), after randomization test by Student's test and Chi² test.

The prevalence rate of asymptomatic FB in our study was 1.6/1000 in the population over the age of 55 years. A statistically significant difference was demonstrated between the two groups in terms of the following parameters: more advanced age for patients of group 1, constant history of root canal treatment in group 1, constant maxillary topography in group 1, and higher recurrence rate in group 2. Mean follow-up was 18.7 months (range: 3–49 months).

This study, the first to determine the prevalence of asymptomatic FB, suggests the existence of very slowly progressive, minimally symptomatic forms, raising the problem of the surgical indications in these patients.

The prevalence of asymptomatic fungus balls is 1.6/1000. Prospective studies are necessary to justify conservative management in these patients.