Psoriasis is an autoimmune disease that is characterized by patches of itchy, scaly, and sometimes inflamed skin.
Although they can appear anywhere, these patches -- called plaques -- are most likely to crop up on the knees, elbows, hands, feet, scalp, or back. According to the American Academy of Dermatology, the fingernails and toenails become pitted in about half of all active psoriasis cases. Up to 30% of people with psoriasis develop psoriatic arthritis, which causes pain, swelling and stiffness in around the joints.
The signs and symptoms of psoriasis vary depending on the type you have. Some common signs for plaque psoriasis -- the most common type of psoriasis -- include:
Plaques of red, inflamed skin, often covered with loose, silver-colored scales. These plaques may be itchy and painful and sometimes crack and bleed. In severe cases, the plaques will grow and merge into one another, covering large areas.
Disorders of the fingernails and toenails, including discoloration and pitting of the nails....
The symptoms of psoriasis can vary a great deal depending on their severity, ranging from mildly annoying to truly debilitating.
While the itchiness can be unpleasant, some of the worst effects of psoriasis can be emotional. People with severe psoriasis sometimes are so overwhelmed by their condition and self-conscious of their appearance that they feel isolated and depressed.
According to the National Psoriasis Foundation, up to 7.5 million Americans have the disease. It has no cure, but there are effective treatments that can keep psoriasis under control.
What Causes Psoriasis?
Skin cells normally are constantly being formed deep beneath the surface of the skin. Over about a month, these cells die and flake off, making way for new skin cells.
If you have psoriasis, skin cell turnover can happen in a matter of days; layers of skin build up, forming a white, flaky crust. Blood vessels increase flow in an attempt to nourish this skin, which leads to redness and swelling. The classic symptoms of psoriasis are reddened, inflamed skin with a whitish, flaky layer of dead cells on top.
Although psoriasis usually appears as a skin condition, recent discoveries show that its real cause is a malfunctioning immune system. Our bodies naturally fight infections and heal injuries with special cells -- called white blood cells -- that battle viruses or bacteria. Normally, these cells go to the site of infection or injury to help repair wounds and prevent infection.
In people with psoriasis, a type of white blood cell, the B-cell, begins creating antibodies that destroy normal skin cells. Another type of white blood cell, the T-cell, begins overproducing a type of protein called a cytokine. This overproduction appears to turn off a signal that controls the growth of skin cells. This is why psoriasis is considered an autoimmune disease -- the individual's immune system attacks normal body tissues. Other autoimmune diseases include lupus and rheumatoid arthritis.
Psoriasis is not contagious. Experts believe there is some hereditary factor in the disease; it seems to run in families.
Types of Psoriasis
There are several different types of psoriasis.
Plaque psoriasis. This is the most common type. About 80% of people with psoriasis have this type. Skin lesions are raised and red, often covered by a silver-colored or white scale. Plaque psoriasis commonly affects the elbows, knees, scalp, and lower back.
Guttate psoriasis. This form of psoriasis usually affects children, teenagers, and young adults. It often appears after an infection, such as strep throat. Its typical symptoms are red, scaly, raindrop-shaped spots on the skin, usually over the abdomen, arms, legs, and scalp. It can often clear up on its own without treatment.
Pustular psoriasis. The typical symptoms of pustular psoriasis are pus-filled blisters on the skin. The blisters usually dry up, turn brown, become scaly, and peel off. The lesions usually occur on the hands and feet and are primarily seen in adults.
Erythrodermic psoriasis. Symptoms include fierce red and scaly skin over large areas of the body. This condition can evolve from other forms of psoriasis or be triggered by psoriasis treatment. It can also be triggered by withdrawal from drugs such as corticosteroids (often taken for diseases such as asthma).
Inverse psoriasis. In people with this condition, scaly and bright red patches appear in folds of skin, for instance under the breasts, in the armpits, or on the genitals. This type of psoriasis can be made worse by obesity.