Introduction: Interstitial lung disease (ILD) in children (chILD) is rare and often severe. This study aims at analyzing the epidemiology of chILD in France from 2000 to 2022.

Methods: This study was retrospective and multicentric. A questionnaire was sent to all the RespiRare centers to collect the clinical, radiological, biological, histological and genetic data of the patients.

Results: 617 patients (0-18 years) were included in 42 centers. 84 patients were excluded. The median age at diagnosis was 0.3 years with 17% of familial forms. The main investigations performed were: chest CT scan (92%), bronchoalveolar lavage (52%), genetic analysis (78%), lung biopsy (23%). The main treatments were: corticosteroids (93%), oxygen therapy (52.2%), enteral nutrition (29%), hydroxychloroquine (16%), azithromycin (26%), immunosuppressive drugs (21%). The follow-up time was from 0 to 18,9 years (median duration 3,5years). The survival rate at 5 years was 68%. The overall incidence and prevalence were estimated at 38/million and 35/million children respectively.

Conclusion: This large chILD epidemiological study confirms the Spanish data with a higher incidence and prevalence than previously described. The large amount of phenotypic data collected will allow better understanding chILD and harmonizing their management.