LAUSR

INTRODUCTION The anti-inflammatory effects of long term low dose macrolide therapy have shown benefit in the management of diffuse panbronchiolitis. Dramatic responses to macrolide in the upper airway are seen but our understanding of the patient phenotype predisposing to macrolide response in chronic rhinosinusitis (CRS) is poor. METHODS A case control study was performed in a tertiary level rhinology practice of consecutive chronic rhinosinusitis patients placed on a 3-month low dose macrolide therapy after failing at least 3 months of corticosteroid irrigation therapy post-endoscopic sinus surgery. Patients were defined as a macrolide responder when having near normal endoscopy after a 3-month period of clarithromycin treatment. Patient characteristics of smoking, asthma, atopy status, revision surgery, symptom severity (SNOT-22) along with biomarkers from serum and tissue histopathology results were compared between groups. RESULTS Of twenty-eight consecutive macrolide treated patients, 19 responders were compared to 9 non-responders. The groups were similar in age, female gender, non-smoking, asthma, and atopy. Macrolide response was associated with a lack of tissue eosinophilia (more than 10/HPF) and lower serum eosinophilia. Neutrophil expression was similar in tissue and serum. Squamous metaplasia was overexpressed in non-responders. CONCLUSION Low tissue and serum eosinophilia, and absence of tissue squamous metaplasia may predict a CRS phenotype suitable to a trial of long-term macrolide therapy when surgery and topical therapy has failed.