Psoriasis is a common, chronic, autoimmune disease that causes dry, red, scaly patches and flakes to appear on the skin. The rash often goes away for a while, but then it flares up again, often as a result of a trigger, such as stress.
It is thought to happen when the immune system mistakenly starts producing skin cells too quickly.
Psoriasis affects around 3 percent of people globally, and around 7.5 million people in the United States (U.S.).
It affects men and women equally. It can begin at any age, but it is most common between the ages of 15 and 35 years, and again between 50 and 60 years. The average age is 28 years.
Around 15 percent of cases emerge before the age of 10 years.
Plaque psoriasis is the most common type of psoriasis.
Skins cells shed all the time, but in psoriasis, both dead and live cells collect on the skin’s surface, because the replacement process is so fast.
The main symptoms of psoriasis are:
red, flaky, crusty patches, covered with silvery scales that shed easily
intense itching and burning
However, symptoms can differ, according to the type. Severity can range from mild to severe.
According to the National Psoriasis Foundation:
mild psoriasis covers less than 3 percent of the body
moderate psoriasis affects between 3 and 10 percent
severe psoriasis covers over 10 percent of the body.
Around 80 percent of people have mild psoriasis, and the other 20 percent have moderate to severe psoriasis.
Psoriasis can affect any part of the body, but it mostly appears as small patches on the elbows, knees, lower back, and scalp.
There are several forms of psoriasis.
About 80 to 90 percent of people with psoriasis have plaque psoriasis. It appears as raised, inflamed, red lesions,
covered by a silvery, white scales, usually on the elbows, knees, scalp, and lower back.
Inverse psoriasis appears in the armpits, the groin, under the breasts, and in other skin folds such as around the genitals, and the buttocks. It first appears as red lesions, usually without the scale associated with plaque psoriasis. It may appear smooth and shiny.
Irritation from rubbing and sweating can make it worse, because of its location in skin folds and tender areas. It is more common in people who are overweight and in those with deep skin folds. It can affect the genital area.
Erythrodermic psoriasis is a particularly inflammatory form that can affect large parts of the body surface with a fiery redness. Erythema means reddening.
It generally appears on people with unstable plaque psoriasis, where lesions are not clearly defined. There may also be exfoliation, or shedding of the skin, severe itching, and pain.
Erythrodermic psoriasis is linked to an imbalance in the body’s homeostasis. This can cause protein and fluid loss that can lead to severe illness.
Edema, or swelling from fluid retention, especially around the ankles, may also develop. The body may have difficulty regulating its temperature, and this can cause shivering.
Erythrodermic psoriasis can also trigger infection, pneumonia, and congestive heart failure.
The complications of erythrodermic psoriasis can be life threatening. Anyone who may have symptoms of this condition should see a doctor at once.
People with severe cases of this condition may spend time in the hospital.
Guttate psoriasis often starts in childhood or young adulthood. It appears as small, red, individual spots on the skin that are not normally as thick or as crusty as the lesions in plaque psoriasis.
A range of conditions can trigger it, including upper respiratory infections, streptococcal infections, tonsillitis, stress, injury to the skin, and the use of certain drugs, including antimalarials, lithium, and beta-blockers.
This form of psoriasis may go away on its own and not come back, or it may clear for a time and reappear later as patches of plaque psoriasis.
Pustular psoriasis affects adults more than children, and it accounts for fewer than 5 percent of psoriasis cases.
It appears as white pustules, or blisters, of non-infectious pus, surrounded by red skin. It can affect certain areas of the body, for example, the hands and feet, or most of the body. It is not an infection, and it is not contagious.
Pustular psoriasis tends to follow a cycle, in which reddening of the skin is followed by the formation of pustules and scaling.
Up to 40 percent of people with psoriasis have joint inflammation with symptoms of arthritis, known as psoriatic arthritis.
This causes inflammation and progressive damage to the joints. It is most common between the ages of 30 to 50 years.
People with psoriatic disease commonly experience social exclusion and low self-esteem. Together with the physical discomfort, itching, and pain of psoriasis, this can impact their quality of life.