Abstract
Objective: To determine the pattern of cellular infiltration of Nasal Polyps (NP) in different Malaysian ethnic groups who co-exist within the same environment.
Methodology: A total of 176 patients with CRS with nasal polyposis (CRSwNP) were included in the study. Disease severity was measured by endoscopic examination and computed tomography (CT) using Lund-Mackay scoring system. The number of eosinophils and non-eosinophils were counted, and average number of inflammatory cells for each high power field was calculated.
Results: Eosinophil-predominant CRSwNP was seen in 35.8% of patients and 64.2% had non-eosinophil-predominant CRSwNP. Non-eosinophil predominant subtypes could be divided into neutrophil (31.3%), plasma cells and others (33%). Phenotypes of CRSwNP showed a significant association with ethnicity (x² = 9.640; p < 0.05). 72% of nasal polyps in Chinese showed non-eosinophil predominance, while nasal polyps in Malays and Indians revealed 69% and 41% of the non-eosinophilic phenotype, respectively. However, no association was demonstrated between phenotype of CRSwNP and recurrence rate for NP, endoscopic staging (bilateral) or CT scores (p > 0.05).
Conclusion: Our study showed Malaysian Chinese and Malay ethnic groups had a non-eosinophilic phenotype of nasal polyps. This was particularly the case in the Malaysian Chinese population.

Key words: Chronic rhinosinusitis, nasal polyps, eosinophil, neutrophil, plasma cells.