PCDH1 and asthma: Genome-wide association studies (GWAS) have confirmed that the genetic predisposition for asthma development is partially associated with barrier dysfunction; single-nucleotide polymorphisms (SNPs) have been identified in multiple genes, including protocadherin-1 (PCDH1), cadherin-related family member-3 (CDHR3), and orosomucoid-like protein isoform-3 (ORMDL3) (53).