Chronic obstructive pulmonary disease (COPD) was the predominant underlying diagnosis (44%), succeeded by cystic fibrosis (15%), idiopathic pulmonary fibrosis and lymphangioleiomyomatosis (each 7%), alpha-1 antitrypsin deficiency (6%), and pulmonary arterial hypertension (4%). This evidence concerns the gene PSMA6 and idiopathic pulmonary fibrosis.