Pediatric-onset bronchiectasis exhibits greater severity than adult-onset bronchiectasis.

<bold>Background:</bold> Bronchiectasis (BE) in children has characteristics unique from adult bronchiectasis, yet its long-term prognosis remains unknown. Our study aims to describe characteristics and prognoses of pediatric-onset bronchiectasis (POBE) compared to adult-onset bronchiectasis (AOBE). <bold>Methods:</bold> This retrospective single-center study compared POBE, defined as the onset of symptoms before or at the age of 18, with AOBE characterized by symptoms appearing after the age of 18. Demographic, microbiological, clinical and lung function were extracted from electronic medical records. Multivariable analysis was employed to compare outcomes. <bold>Results:</bold> 149 patients were included, 49 with POBE and 100 with AOBE, mean age 69.2 years (SD=18.9), 59.7% female. POBE patients were younger (mean, 60.8 vs. 73.4 years, p<0.001). An idiopathic or post-infectious etiology of BE was significantly more common in AOBE group (81.0% vs. 50.0%, p<0.001). Patients with POBE had lower lung function (ppFEV1 at baseline 65.05 vs. 79.51, p<0.001) and a higher exacerbation rate (median exacerbation in the last year of follow-up 2 [0-5] vs. 1 [0-5], p=0.002). FEV1 was inversely correlated with symptom duration only in AOBE (Figure 1). <bold>Conclusions:</bold> Our study shows that POBE patients, despite being younger, have worse physiological and clinical outcomes than AOBE patients, possibly due to different etiologies or longer disease duration.