POSTN and psoriasis: As opposed to atopic dermatitis, in which periostin serum levels are closely related to the severity and activity of the disease14, in psoriasis serum periostin levels did not correlate with the severity of the disease (Supplementary Fig. S2a), even when we looked separately in groups of 15 and > 15 Psoriasis Area Severity Index (PASI) score patients (data not shown).