Although chronic rhinosinusitis (CRS) is a multifactorial disease in a heterogenous group of diseases with different underlying etiologies and pathophysiologies, European and US studies proposed the classification into four categories, i) acute bacterial rhinosinusitis, ii) CRS without nasal polyps, iii) CRS with nasal polyps (CRSwNP), and iv) allergic fungal rhinosinusitis. The histomorphological patterns of CRSwNP are characterized by Th2-driven immune responses including the predominance of eosinophils and mixed mononuclear cells with a relative paucity of neutrophils. Differing from European and US patients, Japanese patients with CRSwNP are thought to be subdivided into eosinophil-dominant, neutrophil-dominant, and eosinophil- and neutrophil-paucity types. The subclassified categories of CRSwNP were evaluated and supported by the clinical backgrounds such as disease severity, atopic status, recurrence, etc. Furthermore, the expression patterns of inflammatory parameters in each group were compared in order to clarify the immunological characteristics.
Treatment strategy for eosinophilic CRS is as follows. Selective patients showing extensive and massive sinonasal pathology were prescribed a 7-day course of oral predonisolone tablets before and/or after endoscopic sinus surgery (ESS). A short-term (3 to 5 days) of oral predonisolone was prescribed when olfactory acuity judged by self smell test was aggravated. Moreover, antibiotics were orally given in the presence of massive purulent nasal discharge. Bacterial infection may play a critical role of recurrent polyps and refractory symptoms during post-ESS follow-up. Moreover, worsening of sinusitis accompanies asthma exacerbation.

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Nitric oxide (NO) has a variety of roles in human airways relevant to airway defense mechanisms, as well as being an inflammatory mediator. The standardization of measurements by the American Thoracic Society/European Respiratory Society has opened the gate for the accumulation of comparable fractional concentrations of exhaled NO (FeNO) data in normal subjects and diseased patients. Although the human paranasal sinuses are known to be a major source of intrinsic NO production, there are several issues to be solved before FeNO measurement becomes a reliable and valid marker for the diagnosis of allergic rhinitis (AR) and chronic rhinosinusitis (CRS). They include 1) complicated anatomical structure of paranasal sinuses and gas exchange through the narrow sinus ostia, 2) the balance between maintaining optimal mucociliary clearing function by the ciliary epithelium and modulating inflammatory conditions by excess NO production, 3) inhibitory effects of gaseous NO diffusion into the air-filled sinus caused by excess secretions and thick aqueous epithelial lining in case of sinusitis. AR patients have been considered to be associated with increased FeNO levels mainly by the increased expression of inducible nitric oxide synthase (iNOS) in the inferior turbinate. Nasal NO levels generally decrease in most CRS patients. However, it is unclear to what extent nasal NO levels contribute to sinusitis pathology especially pertinent to different CRS types. We have recently shown that higher FeNO levels in ECRS patients closely correlate with augmented iNOS expression and are accompanied by the excretion of NO metabolites into the paranasal sinus mucosa.

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As shown in the concept of ‘one airway, one disease’, there is a close relationship between the upper and lower airways and the possibility for the development of airway inflammation. In many cases of the patients with eosinophilic sinusitis also developed the adult onset asthma. Otorhinolaryngologists and physicians of internal medicine evaluate upper and lower respiratory tracts separately. It is a very important to identify the objective biomarkers which show the severity of the disease in both upper and lower airways.
In the present study, the number of eosinophils did not reflect the severity of eosinophilic sinusitis, however, it showed some correlation with that of pulmonary function. In addition, the saccharin time which reveals the mucus ciliary function, was deteriorated in the patients with eosinophilic sinusitis. Interestingly, the sinus operation resulted in improvement of the pulmonary function of the patients with eosinophilic sinusitis. The sinus operation might be expected to be useful as an early intervention for the treatment of adult onset asthma.

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