Major basic protein deposited at intra mucosal epithelium with probable eosinophilic chronic rhinosinusitis.

Background: Eosinophilic chronic rhinosinusitis (ECRS) is diagnosed by Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis (JESREC) scoring system and histopathological eosinophil counts of dissected nasal polyps. Patients with low JESREC score and small number of tissue eosinophils are diagnosed with non-ECRS (NECRS). Due to the 2 parameters of this diagnostic system, chronic rhinosinusitis is to be divided to 4 groups and some patients fall into the 2 groups other than ECRS and NECRS: probable ECRS (pECRS) and probable non-ECRS (pNECRS). We attempted to clarify clinical and histopathological similarities and differences, especially concerning major basic protein (MBP), among those groups.

Methods: One hundred twenty-eight patients treated by endoscopic sinus surgery was included. Clinical characteristics were compared among each group, and immunohistological analysis for MBP was performed to 35 randomly selected patients. MBP deposition at intra mucosal epithelium was evaluated by semiquantificational approach.

Results: ECRS patients showed significantly higher comorbidity rate with allergic rhinitis (36 patients, 78.3%), asthma (36 patients, 78.3%) compared with other groups. Also, percentage of the patients complaining olfactory dysfunction (42 patients, 91.3%) was significantly higher (p < 0.001). Lund-Mackay score (mean, 14.5; 6-24) and recurrence rate (27 patients, 61.4%) was the highest in ECRS patients. Regarding pECRS, the number of patients with olfactory dysfunction (5 patients, 55.6%) was higher than pNECRS and NECRS groups. Also, comorbidity of asthma and percentage of blood eosinophils tended to be higher than those 2 groups. MBP score of pECRS group was significantly higher than NECRS (p < 0.05), despite of smaller tissue eosinophil counts.

Conclusion: pECRS might share some characteristics with ECRS although tissue eosinophil count was significantly smaller compared with ECRS. The results of this study have shown that MBP score in pECRS nasal polyps was significantly higher than NECRS patients and close to ECRS. That might suggest that eosinophils have existed in the nasal polyps of pPECRS patients at some point before surgery.