Single-plex assays of the type 2 inflammatory biomarkers demonstrated significantly elevated circulating plasma IL-13 (0.13 vs. 0.006 pg/mL, p = 0.0008) and periostin (80.3 vs. 60.2 ng/mL, p = 0.012) in PN patients compared to controls. This evidence concerns the gene POSTN and poikiloderma with neutropenia.