A double blind, randomised, placebo-controlled trial to evaluate the doseexposure and safety of nintedanib per os on top of standard of care for 24 weeks, followed by open label treatment with nintedanib of variable duration, in children and adolescents (6 to 17 year-old) with clinically significant fibrosing Interstitial Lung Disease. (Boehringer Interstitial Lung Disease (ILD) 1199-0337).