Comparative Analysis of Small and Large Plaque Psoriasis
Condition: Psoriasis
MeSH terms: Psoriasis
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      Psoriasis is a common chronic skin disorder with an estimated prevalence in populations of
      approximately 2%. Psoriatic skin lesions start with initial pinhead-sized macules and then
      coalesce into plaques of varying sizes in diameter from one to several centimeters.

      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. The occurrence of
      psoriasis is thought to be the pathological consequence of an exaggerated immune response as
      activated T cells, monocytes, neutrophils, and dendritic cells produce inflammatory cytokines
      that drive the additional recruitment of inflammatory cells, further elaboration of
      proinflammatory mediators, and the proliferation of keratinocytes. However, pathogenetic
      mechanism for peripheral spreading of psoriasis needs to be further elucidated.

      To study peripheral spreading of psoriasis, investigators plan to study "small plaque
      psoriasis" and compare it to "large plaque psoriasis" in the Korean population.

      Psoriasis vulgaris, so-called "large plaque psoriasis", is the most common form of psoriasis,
      seen in approximately 90% of all psoriasis patients. Red, scaly, symmetrically distributed
      plaques are usually larger than 5 cm in diameter and characteristically localized to the
      extensor aspects of the extremities, particularly the elbows and knees, along with scalp,
      lower lumbosacral, buttocks, and genital involvement. Approximately 1/4 to 1/3 of large
      plaque psoriasis participants have involvement of over 5% of their body surface area (BSA),
      and disease of this extent is frequently painful and physically and/or socially debilitating
      to a degree comparable with other chronic medical conditions.

      On the other hand, "small plaque psoriasis" is the common or typical form of psoriasis that
      occurs in adults particularly in Korea and other Asian countries. Korean small plaque
      psoriasis, even when chronic, remain <2 cm in size and widely distributed on upper trunk and
      proximal extremities. Small plaque psoriasis is less severe than large plaque psoriasis, as
      it usually responds to phototherapy and more potent therapies are rarely needed.

      It is also noteworthy that there are well-known human leukocyte antigen (HLA) differences in
      Caucasians in comparison with Asian participants with psoriasis, and a unique HLA haplotype
      has been described in Korean participants with psoriasis. Furthermore, an allele of an
      HLA-related gene, known as major histocompatibility complex I chain-related gene A, is known
      as a susceptibility marker in Korean and Chinese participants with psoriasis, but not in
      Spanish participants.

      For a more comprehensive analysis of the difference between small and large plaque psoriasis,
      investigators plan to compare these two different types of psoriasis only in the Korean
      population. 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 Korean psoriasis participants in two geographically separated
      locations (Seoul, Korea vs. New York, NY, USA), it will also be interesting to understand the
      interactions between genetics and the environment that are still not well defined.

      It is anticipated this study could lead to new understanding of the mechanisms involved in
      the spreading of psoriatic plaques and provide new insight into psoriasis pathogenesis.
    

Intervention name(s): Skin biopsy and blood test
Intervention type(s): Procedure
Intervention description(s): Analysis of histology and gene expression in affected and unaffected skin
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Psoriasis; Korean; Healthy Volunteers