1.3 Allergy and recurrent acute rhinosinusitis (RARS) in children.
We found very limited and heterogeneous data linking allergy to RARS and it was not possible to perform a qualitative analysis. Choi et al.(34) evaluated the predisposing factors that may be associated with chronic and recurrent RS examining 296 patients with RS younger than 13 years of age. The prevalence of allergic rhinitis, atopy, and asthma were significantly higher in patients with chronic and recurrent RS than those with acute and subacute RS. Veskitkul et al.(35) evaluated the clinical characteristics and predisposing factors of RARS in children as well as the preventive therapy. The authors suggested that allergic rhinitis may be considered a predisposing factor because it was detected in 35.1% of cases, concluding that children with RARS should be always evaluated for the presence of underlying predisposing conditions including allergic disease. Nevertheless, no comparison with a control group was performed and for this reason data are not definitely supporting a link between allergy and RARS.
Allergy and Chronic Rhinosinusitis (CRS) in Children.
Chronic rhinosinusitis (with or without nasal polyps) in children is defined as: presence of two or more symptoms, one of which should be either nasal blockage/obstruction/congestion or nasal discharge (anterior/posterior nasal drip) with or without facial pain/pressure and/or cough for ≥12 weeks associated to pathognomonic endoscopic signs or CT changes(7). The prevalence of CRS in children is lower than in adults (2-4%), nevertheless, the negative impact on quality of life seems to be similar to that observed in adults. Studies on CRS in children are less common and it is more difficult to investigate the relationship with allergy(7). Several factors contribute to complicate the analyses including incomplete evaluation (nasal endoscopy and/or imaging are rarely performed in many children) and the difficulty to differentiate CRS from adenoid hypertrophy, adenoiditis, and (allergic) rhinitis. In fact, nasal blockage may occur in AR children, due to edematous mucosa, neurogenic and vascular responses, over-production of secretions, and impaired muco-ciliary clearance leading to congestion of the ostia and symptoms simulating rhinosinusitis. On the other hand, the blockage leads to stagnant debris and acidotic environment that might stimulate bacteria overgrowth(36, 37).
Histopathological analysis(38,39) demonstrated that pediatric CRS is quite different from the adult form, showing greater inflammatory cellularity, higher density of submucosal lymphocytes, less eosinophilic inflammation, basement membrane thickening, and mucous gland hyperplasia, suggesting a different pathway compared to the adult CRS pattern, which is predominantly characterized by a Th2-oriented response with polypoid changes. The presence of nasal polyps in a pediatric patient should suggest the hypothesis of cystic fibrosis that has not been included in this paper. More specifically, some evidence supports the hypothesis that CRS in children over the age of 13 seems to be based more on eosinophilic inflammation, while under this age CRS seems to be based more on neutrophilic inflammation, thus justifying the lower prevalence of nasal polyps in children than in adult(38, 39).
Several manuscripts support the hypothesis that AR and CRS could be different faces of the same disease. AR, in fact, is typically characterized by a Th2 immune response involving IL-4, IL-5 and IL-13 which drives IgE production and recruitment of eosinophil granulocytes. It has been suggested(40-44) that eosinophils, by generating potent toxic agents (cationic proteins, oxygen-free radicals, and proinflammatory cytokines), may play a major role in initiating and perpetuating inflammation of sino-nasal mucosa in patients with AR.