Statistics vary, but current estimates indicate that 2% to 3% of the U.S. population, or around 5 to 7 million adults, have some psoriasis on their skin. Approximately 200,000 people are newly diagnosed with psoriasis each year. The prevalence rate varies in different ethnic groups and is higher in Caucasians than in blacks, Hispanics, Asians, and Native Americans. The reasons for different prevalence rates are not known but are believed to be due to the association with certain genetic backgrounds . Because psoriasis appears for the first time in the majority of people while in their 20s, it is found less often in children, and new diagnoses are even rarer in older people.
Because psoriasis is less common in children and older people, a psoriasis diagnosis in these individuals may not be immediately clear. Among people who have psoriasis, psoriasis vulgaris (vulgaris meaning common), or plaque psoriasis, is the most common form, found in over 85% of people with psoriasis (see color plate G). The other types of psoriasis comprise around 15% of cases, though people may have more than one type at the same time. One type of psoriasis, guttate psoriasis, is more commonly found in children after a throat, skin, or other infection and sometimes resolves after the infection is treated.
Because these rarer types of psoriasis look different than the common type, they may be undiagnosed or misdiagnosed in some individuals for a period of time. The incidence of psoriasis worldwide varies somewhat but is generally in the 2% to 5% range. The highest incidence is estimated at 10% among people from northern Europe and is the lowest in parts of South America and Samoa where no psoriasis has been reported. Women and men are equally affected by psoriasis.
For people with psoriasis, approximately 5% to 30% may develop psoriatic arthritis, and this is more likely to occur in people with more severe disease. For most people, arthritis appears 5 to 10 years after skin psoriasis, though in a small group of people it may be the first sign of psoriasis.
John’s comment:
Most people tend to hide their psoriasis, and accordingly, it seems like I am the only person in the world with psoriasis. It is great to know that I am not alone. There are probably more people in the United States with psoriasis than inhabitants of Los Angeles. I just wish we were all more open about it, so it might become more accepted and better understood by society at large.