Further supporting this, recent studies demonstrated that the gain-of-function MUC5B promoter variant rs35705950 initially observed in IPF [14], was also associated with fibrotic hypersensitivity pneumonia and RA-related UIP and to a worse outcome [15], while this was not the case in other ARDs [16–18]. This evidence concerns the gene MUC5B and idiopathic interstitial pneumonia.