The prevalence of reactive nasal inflammatory conditions, for example, allergic rhinitis and chronic rhinosinusitis, is steadily increasing in parallel with significant environmental changes worldwide. Allergens and as yet undefined environmental agents may trigger these conditions via the involvement of host intrinsic factors, including the innate and adaptive immune system, the nasal epithelium, and the nasal nervous system. The critical role of the nasal microbiota in coordinating these components has emerged in recent studies documenting a significant association between microbial composition and the onset and progression of allergic or nonallergic inflammation. It is now clear that the local microbiota is a major player in the development of the mucosa-associated lymphoid tissue and in the regulation of such adaptive responses as IgA production and the function of effector and regulatory T cells. Microbial components also play a major role in the regulation of epithelial barrier functions, including mucus production and the control of paracellular transport across tight junctions. Bacterial components, including lipopolysaccharide, have also been shown to induce or amplify neuroinflammatory responses by engaging specific nociceptors. Finally, bacterial products may promote tissue remodeling processes, including nasal polyp formation, by interacting with formyl peptide receptors and inducing the expression of angiogenic factors and matrix-degrading enzymes.

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Background Maxillary sinus hypoplasia (MSH), associated with enophthalmos and hypoglobus in the silent sinus syndrome (SSS), is a poorly studied condition. The real incidence of MSH and SSS in the adult population is not known. Our study aims at estimating the radiological prevalence of MSH and identifying undiagnosed cases of SSS in a retrospective cohort. Methods A cross-sectional retrospective cohort study was performed in adults, without a history of maxillofacial surgery or trauma, undergoing head CT scans. A radiological database of 1012 consecutive scans was reviewed independently by two authors to identify patients with signs of MSH and SSS and associated findings (septal deviation, uncinate deviation, concha bullosa, sinus opacification, bony rarefaction, and pterygopalatine fossa enlargement). The findings of MSH and SSS were compared with radiological reports. Results 891 eligible CT scans were analyzed. MSH and SSS prevalences were 6.17% (n = 55) and 0,56% (n = 5), respectively. The maxillary sinus was normally or partially ventilated in 96.36% of MSH patients. Lateralization of the uncinate process was detected in about 50% of MSH patients, while a septal deviation towards the affected sinus was detected in 21.82%. In 20% of MSH scans, a concha bullosa was identified. Radiological reports identified a single MSH case. Conclusions Our study confirmed the literature data on MSH prevalence, while it determined a precedently unknown prevalence for SSS, underestimated in the radiology reports. This prevalence needs further confirmation but suggests a routine accurate comparison of both maxillary sinuses in CT scans.