SFTPD and allergic disease: The lung surfactant protein named Clara Cell protein 16 (CC16) and the surfactant protein D (SP-D) secreted by the lung epithelium has been used as indicators to detect short-term changes in lung epithelial integrity [16]–[18] that can produce inflammation of the airways, increased sensibility and allergic diseases, produced by the high permeability of the epithelial barrier [19].