POSTN and psoriasis: Periostin levels were decreased by 37% in plasma from patients with psoriasis in our study, which stands in contrast to a recent finding by Wojciechowska et al., who found periostin to be highly upregulated in serum from patients with psoriasis, although they at the same time showed a tendency towards a negative correlation between the Psoriasis Area and Severity Index (PASI) and periostin [19].