Eosinophil degranulation patterns in nasal polyposis: an ultrastructural study.

Background: Eosinophils are possibly the most important inflammatory cells in the pathogenesis of rhinosinusitis with nasal polyposis. Eosinophil degranulation is the mechanism by which these cells exert their inflammatory action. Knowledge of eosinophil state and degranulation mode therefore may help us to better understand this disease. A study is made of eosinophil state and degranulation mode using transmission electron microscopy (TEM), attempting to establish correlations with certain clinical variables considered to be of importance in patients with nasal polyposis.

Methods: A prospective TEM study was made to examine 582 eosinophils under 5000x magnification, classifying them according to their state and degranulation mode. The cells originated from 36 cases of nasal polyposis and were catalogued according to the clinical-radiological presentation of the disorder, the presence of asthmatic disease, or acetilsalicilic acid (ASA) triad syndrome (nasal polyposis, asthma, and nonsteroidal anti-inflammatory drug intolerance), and the degree of nasal tissue eosinophilia of the case of origin.

Results: A total of 30.75% of the eosinophils were inactive, 41.75% exhibited piecemeal degranulation (PMD), 27.5% exhibited cytolysis, and 0.34% were in apoptosis. The degranulation mode was significantly correlated to the clinical and histological parameters studied. Thus, cytolysis tended to be less pronounced and PMD greater, in the cells from cases with intense eosinophilia or severe polyposis (high clinical stage and ASA triad).

Conclusion: Cytolysis and PMD are the principal degranulation modes of eosinophils in nasal polyposis-apoptosis being very infrequent. Nasal polyposis shows a correlation between eosinophil degranulation mode and the clinical and radiological stage and the degree of tissue eosinophilia of the case of origin.