SFTPD and cystic fibrosis: Lin et al. [89] investigated the genetic contribution of SFTPA1, SFTPA2, SFTPB, SFTPC, and SFTPD genes to CF and lung disease severity; they identified, between single-nucleotide polymorphisms (SNPs) and several intragenic and intergenic SNP-SNP interactions, a single SFTPB SNP that was associated with a mild CF (rs7316), and several intergenic interactions that are associated with either mild or moderate/severe CF were observed (Table 2).