Comparative Analysis of Small and Large Plaque Psoriasis

Psoriasis is a chronic, debilitating skin disorder with an estimated prevalence of 2%. Psoriatic skin lesions start with initial pinhead-sized macules and then coalesce into plaques of varying sizes. Despite the great strides in the studies for psoriasis, it is still unclear why psoriatic skin lesions start with small macules and then spread peripherally. To study peripheral spreading of psoriasis, investigators plan to study small plaque psoriasis in comparison to large plaque psoriasis in the Korean population. Large plaque psoriasis is the most common form of psoriasis, seen in approximately 90% of all psoriasis participants. Large psoriatic plaques are \>5 cm in size and localize to the extensor aspects of the elbows, knees, scalp, and genital area. On the other hand, small plaque psoriasis is the common or typical form of psoriasis that occurs particularly in Korea and other Asian countries. Korean small plaque psoriasis, even when chronic, remains \<2 cm in size and is widely distributed on the upper trunk and proximal extremities. Investigators hypothesize that the expression of immune-related genes are different between small and large plaque psoriasis. The study of a genetically homogeneous cohort, characterized by the relatively high prevalence of small plaque psoriasis in the Korean population, may filter out spurious signals while allowing for significant associations to emerge from a relatively low number of participants. By comparing small and large plaque psoriasis, it is expected this study could lead to new understandings of the mechanisms involved in spreading of psoriatic plaques and provide new insights into psoriasis development.