Does molecular scarring in psoriasis exist? A review of the literature

Plaque psoriasis is a chronic inflammatory dermatosis characterized by a tendency to recur in the same locations after discontinuation of treatment. The implementation of therapy with drugs targeting cytokines like interleukin (IL) 17A (IL-17A) and IL-23 has revolutionized the treatment of psoriasis and enabled the achievement of skin without lesions. However, despite the clinical resolution of psoriatic eruptions, cells that maintain the local memory of the disease remain in the dermis and epidermis, constituting a kind of molecular scar. The cells responsible for maintaining memory in the skin of patients and influencing the rapid relapse of the disease after the triggering factor are primarily tissue resident memory T cells (TRM), but it seems that regulatory T lymphocytes (Treg), dendritic cells (DC), and Langerhans cells (LC) may also play an important role in this process. We reviewed the literature to explain the concept of molecular scarring in psoriasis, and to assess the effect of various therapies on immune memory.