In our group, as previously published, multiple genes are associated with CF clinical severity, including Transforming growth factor beta 1 (TGF-β1) [11], Glutathione S-transferase Mu 1 (GSTM1), Glutathione S-transferase Theta 1 (GSTT1) [12], Angiotensin-converting enzyme (ACE) [13] and Beta-2-Adrenergic Receptor (ADBR2) [14] genes as possibly modifier genes. Here, GSTM1 is linked to cystic fibrosis.