VDR and respiratory system disorder: The recent discovery that the vitamin D receptor (VDR) is ubiquitously expressed in nearly every cell type in human tissue has led to the realization that vitamin D also has extraskeletal effects (Bouillon et al. 2008) and there is now a large body of evidence linking vitamin D deficiency to chronic conditions, including autoimmune, infectious, cardiovascular, and respiratory disease (Munger et al. 2006; Holick 2007; Ginde et al. 2009; Anderson et al. 2010; Chinellato et al. 2011).