MMP9 and palmoplantar pustulosis: In the present study, we measured plasma levels of dynorphin A and β-endorphin as well as serum levels of LCN-2, MMP-9, and the MMP-9/LCN-2 complex and investigated their relationships with itch severity in pruritic skin diseases, such as AD, PSO, prurigo nodularis (PN), urticaria, palmoplantar pustulosis (PPP), and asteatotic dermatitis (AsD).