Numerous mast cell-associated mediators and receptors, including IL-4, IL-13, IL-31, Mas-related G protein-coupled receptor member X2 (MRGPRX2), and protease-activated receptor 2 (PAR2), have also been implicated in the pathogenesis of PN [6,40,60]. The gene discussed is F2RL1; the disease is poikiloderma with neutropenia.