POSTN and Nasal polyposis: NP, nasal polyp; IT, inferior turbinate; POSTN, periostin; ALOX15, arachidonate 15-lipoxygenase; CST1, cystatin SN; SERPINB3, serpin peptidase inhibitor, clade B (ovalbumin), member3; CCL18, C-C motif chemokine ligand 18; BPIFA1, BPI fold containing family A member 1; SLPI, secretory leukocyte peptidase inhibitor; BPIFB1, BPI fold containing family B member 1; STATH, statherin; LTF, lactotransferrin.