Novel concepts in psoriasis: histopathology and markers related to modern treatment approaches.

Psoriasis is a chronic autoimmune disease affecting over 2% of the worldwide population. From an anatomopathological point of view, psoriasis is characterized by immune cells infiltration, epidermal hyperproliferation, and abnormal keratinocyte differentiation. Understanding the pathogenesis of psoriasis will allow clinicians to manage this complex disease. Under these conditions, the application of effective treatments requires a thorough knowledge of all the pathogenetic mechanisms that lead to psoriasis. Numerous immunopathological pathways play crucial roles in the development of new therapies, such as biological therapies, which have been a breakthrough in psoriasis's treatment. Pharmacogenetics is an essential factor in the patient's response to treatment. One important pathway targeted by modern treatments is the interleukin (IL)-23∕T-helper (Th)17 axis. Like IL-17 inhibitors, IL-23 blockers are a very effective therapy for this autoimmune disease. It is considered that micro-ribonucleic acids (microRNAs) are the starting point for any autoimmune disease. Studying certain microRNA (miR) involved in the inflammatory pathway in psoriasis can find direct targets to future treatments that can even be more specific than actual biological therapies. As such, miR-210 has proven to be up-regulated in psoriasis, also leading to the up-regulation of the Th1∕Th17 axis. On the other hand, miR-187 was found to be down-regulated, influencing the outcome of psoriasis by increasing the proliferation of IL-6 stimulated keratinocytes and consecutively generating epidermal thickening. In this review, we are aiming to do an up-to-date briefing of psoriasis histopathology and pharmacogenetic factors that are considered for the accurate evaluation of treatment response.