PCDH1 and asthma: We conclude that while decreased PCDH1 might contribute to airway epithelial dysfunction in asthma, altered PCDH1 expression levels do not seem to be a shared mechanism in all asthma patients, and further research will need to address whether loss of PCDH1 contributes to airway epithelial barrier dysfunction in those asthma patients carrying the asthma-susceptible PCDH1 allele.