TGFB1 and Airway obstruction: Our main results are: (1) airway smooth muscle content, collagen content, the degree of small airway closure, and TGF-β epithelial expression are increased in LAM; (2) As expected, the morphological parameter of LAM severity (LHS) is associated with functional changes related to airway obstruction, air trapping and reduced DLCO; (3) small airway wall thickness is higher in patients with more severe disease and is associated with parameters of airflow obstruction and collagen content; (4) Bronchiolar inflammation was mild; infiltration of the small airways wall by LAM cells was rare.