Psoriasis
A chronic immune-mediated disease in which a self-sustaining T-cell/keratinocyte loop drives massive epidermal overproliferation, producing well-demarcated scaly plaques that respond to therapies aimed at that loop.
First principles
Psoriasis is runaway keratinocyte proliferation driven by a fixed immune loop
Normal epidermis renews over about a month. In psoriasis a self-reinforcing immune circuit (dendritic cells activating T-helper-17 cells, which release IL-17, IL-22 and TNF-alpha, which in turn drive keratinocytes to proliferate and to recruit more immune cells) compresses that turnover to a few days. The keratinocytes divide far faster than they can mature. Everything visible in psoriasis follows from this single fact: an epidermis being manufactured at many times its normal rate.
Educational content pending clinical review. Not medical advice.