About psoriasis

Psoriasis is a chronic, systemic, inflammatory skin disease associated with a significant physical and psychological burden.1

Psoriasis affects approximately 8 million people in the US and 125 million people worldwide.2 Plaque psoriasis, also called psoriasis vulgaris, is the most common form and affects about 80–90% of people with psoriasis.1,3,4

The typical age of onset is 15–25 years, but psoriasis can develop at any age.2 People with psoriasis are at an increased risk of developing other chronic and serious health conditions. Comorbidities include psoriatic arthritis, inflammatory bowel disease, hypertension, diabetes, obesity, and depression.3 Psoriasis has a significant impact on quality of life and on psychological health.1,3 Nearly 60% of people with psoriasis consider the disease to be a large problem in their everyday life.5

Figure 1. Psoriasis plaques

Clinical features of psoriasis

Psoriasis is a chronic disease that can wax and wane, with periods of worsening and periods of milder symptoms or remission.3 It is not contagious and cannot be transmitted by touching someone who has it.1 Plaque psoriasis is characterized by raised, red patches of skin, often with silvery scales (Figure 1).1,3 Plaques can vary in size and may join into a larger area if multiple plaques are close to each other.2,3 Plaques can appear in a few areas or all over the body.1,3 Psoriatic plaques most commonly occur on the scalp, trunk, buttocks, and limbs (e.g. elbows, knees, fingernails, and toenails), affecting both sides of the body in a symmetrical distribution.1,3

Psoriasis plaques can be itchy, painful, and disfiguring, and cause significant emotional and physical distress.1,3 About 80% of patients with plaque psoriasis have mild to moderate disease, with the remaining 20% having moderate to severe disease.3,6

Causes of psoriasis

Psoriasis is a complex autoimmune disease, meaning that the body’s immune system targets and attacks its own cells. The autoimmune disease process involves immune cells and proteins involved in the development of inflammation, such as cytokines, tumor necrosis factor (TNF)-α, interferon-γ, and interleukin (IL)-17, and leads to over-production of skin cells and inflammation.1

Psoriasis has a genetic link, as it is more common in people who have family members with the disease.1 People with a family history of psoriasis also have more severe psoriasis that starts earlier than those with no family history.1

Useful links

American Academy of Dermatology Psoriasis Resource Center International Psoriasis Council

Dermavant is not responsible for the website content of external links.


  1. Boehncke WH, Schon MP. Psoriasis. Lancet. 2015;386(9997):983–994.
  2. National Psoriasis Foundation. https://www.psoriasis.org/about-psoriasis/. Accessed November 2020.
  3. Menter A, Gottlieb A, Feldman SR, et al. Guidelines of care for the management of psoriasis and psoriatic arthritis: Section 1. Overview of psoriasis and guidelines of care for the treatment of psoriasis with biologics. Journal of the American Academy of Dermatology. 2008;58(5):826–850.
  4. Mease PJ, Gladman DD, Papp KA, et al. Prevalence of rheumatologist-diagnosed psoriatic arthritis in patients with psoriasis in European/North American dermatology clinics. Journal of the American Academy of Dermatology. 2013;69(5):729–735.
  5. Keating GM. Apremilast: A Review in psoriasis and psoriatic arthritis. Drugs. 2017;77(4):459–472.
  6. Jashin J. Wu, Minyi Lu, Karen A. Veverka, Maartje Smulders, Eros Papademetriou, Junhua Yu & Steven R. Feldman (2019) The journey for US psoriasis patients prescribed a topical: a retrospective database evaluation of patient progression to oral and/or biologic treatment, Journal of Dermatological Treatment, 30:5, 446-453, DOI:10.1080/09546634.2018.1529386.

The information presented on this website is intended for educational purposes only. Readers are encouraged to consult their healthcare providers for further information.