Psoriasis is an inflammatory skin condition. More than 4.5 million adults in the United States have been diagnosed with psoriasis, and approximately 150,000 new cases are diagnosed each year. Psoriasis occurs about equally in males and females.
The exact cause of psoriasis remains unknown. Researchers now believe that psoriasis is an immune-mediated condition. This means the condition is caused by faulty signals in the body’s immune system. It is believed that psoriasis develops when the immune system tells the body to over-react and accelerate the growth of skin cells. Normally, skin cells mature and are shed from the skin’s surface every 28 to 30 days. When psoriasis develops, the skin cells mature in 3 to 6 days and move to the skin surface. Instead of being shed, the skin cells pile up, causing the visible lesions. In addition, recent studies show that there may be an ethnic link. It seems that psoriasis is most common in Caucasians and slightly less common in African Americans. Worldwide, psoriasis is most common in Scandinavia and other parts of northern Europe. It appears to be far less common among Asians and is rare in Native Americans. There also is a genetic component associated with psoriasis. Approximately one-third of people who develop psoriasis have at least one family member with the condition.
Signs and symptoms of psoriasis usually appear between 15 and 35 years of age. About 75% develop psoriasis before age 40. However, it is possible to develop psoriasis at any age. About 1 in 10 people develop psoriasis during childhood, and psoriasis can begin in infancy. The earlier the psoriasis appears, the more likely it is to be widespread and recurrent. After age 40, a peak onset period occurs between 50 and 60 years of age.
There are five types, each with unique signs and symptoms. Plaque psoriasis is the most common type of psoriasis. About 80% of people who develop psoriasis have plaque psoriasis, which appears as patches of raised, reddish skin covered by silvery-white scale. These patches, or plaques, frequently form on the elbows, knees, lower back, and scalp. However, the plaques can occur anywhere on the body. The other types are guttate psoriasis (small, red spots on the skin), pustular psoriasis (white pustules surrounded by red skin), inverse psoriasis (smooth, red lesions form in skin folds), and erythrodermic psoriasis (widespread redness, severe itching, and pain).
Psoriatic arthritis develops in roughly one million people across the United States, and 5% to 10% experience some disability. Psoriatic arthritis usually first appears between 30 and 50 years of age — often months to years after skin lesions first occur. However, not everyone who develops psoriatic arthritis has psoriasis. About 30% of people who get psoriatic arthritis never develop the skin condition.
Regardless of type, psoriasis usually causes discomfort. The skin often itches, and it may crack and bleed. In severe cases, the itching and discomfort may keep a person awake at night, and the pain can make everyday tasks difficult.
Psoriasis is a chronic, meaning lifelong, condition because there is currently no cure. Living with this lifelong condition can be physically and emotionally challenging. People often experience flares and remissions throughout their life. Controlling the signs and symptoms typically requires lifelong therapy.
Treatment depends on the severity and type of psoriasis. Some psoriasis is so mild that the person is unaware of the condition. A few develop such severe psoriasis that lesions cover most of the body and hospitalization is required. These represent the extremes. Most cases of psoriasis fall somewhere in between. Therapies for the control of psoriasis are available and range from topical creams to injectable medications depending upon the severity of each patient’s psoriasis.
