Background: Pediatric and adult bronchiectasis have different clinical profiles but data on long-term follow-up of children with bronchiectasis are scarce. We compared the aetiologies and outcomes of adults with pediatric-onset (paed-BE) bronchiectasis compared with adult-onset (adult-BE) bronchiectasis in the EMBARC registry.

Methods: Patients ?47 years old were included. People with paed-BE bronchiectasis were defined as adults with a bronchiectasis diagnosis made ?20 years ago, and adult-BE as diagnosis made <20 years ago. We compared data on demography, aetiology and severity measures between paed-BE and adult-BE.

Results: 663 adults with paed-BE and 1237 with adult- BE were included. Compared to adult-BE, Paed-BE were younger (median (IQR) 28(22-36) vs. 37(32-41) years) and more likely to be never smokers (85.7% vs. 66.6%, p<.001). Rhinosinusitis and nasal polyps were more common in paed-BE than in adult-BE (41.6% vs. 27.6% and 18.8% vs. 10.3%, respectively, p<.001) while asthma was more common in adult- BE (36.4% vs. 26.8%). Paed-BE were more likely to have an aetiology of PCD: 29.4% vs. 6.8% (p<.001), and less like to have an idiopathic aetiology (27.5% vs. 37.2%, p<.001). Patients with paed-BE had lower lung function and worse severity than adult- BE: median FEV₁% 74.0(50.1-91.3) vs. 84.6(63.4-100.7), BSI 4(2-8) vs. 3(1-6). Paed-BE had a higher risk of exacerbations when adjusted for age, sex, Pseudomonas infection, %FEV₁, Inhaled antibiotic use, macrolide use, asthma and smoking: HR 1.59(1.30-1.94).

Conclusions: despite younger age, patients with paed-BE have worse outcomes than adult- BE. This may be attributed to different aetiologies or to longer disease duration.