Psoriasis is a persistent skin disorder in which there are red, thickened areas with silvery scales, most often on the scalp, elbows, knees, and lower back. Some cases of psoriasis are so mild that people don’t know they have it. Severe psoriasis may cover large areas of the body. Dermatologists can help even the most severe cases.
Psoriasis is not contagious and cannot be passed from one person to another, but it is most likely to occur in members of the same family. In the United States, two out of every hundred people have psoriasis (four to five million people). There are approximately 150,000 new cases that occur each year.
What causes psoriasis?
The cause is unknown. However, recent discoveries point to an abnormality in the functioning of special white cells (T-Cells) which trigger inflammation and the immune response in the skin. Because of the inflammation, the skin grows too rapidly. Normally, the skin replaces itself in about 30 days, but in psoriasis, the process speeds up and replaces the skin in three to four days, and the signs of psoriasis develop.
People often notice new spots 10 to 14 days after the skin is cut, scratched, rubbed, or severely sunburned (Koebner Phenomenon). Psoriasis can also be activated by infections, such as strep throat, and by certain medicines (beta blockers, lithium, etc.) Flare-ups sometimes occur in the winter, as a result of dry skin and lack of sunlight.
Types of Psoriasis
Psoriasis comes in many forms. Each differs in severity, duration, location, shape, and pattern of the scales. The most common form, called plaque psoriasis, begins with little red bumps. Gradually, these become larger, and scales form. While the top scales flake off easily and often, scales below the surface stick together. These small red areas can enlarge.
- Scalp, elbows, knees, legs, arms, genitals, nails, palms, and soles are the areas most commonly affected by psoriasis. It will often appear in the same place on both sides of the body
- Scalp psoriasis may be mistaken for dandruff
- Nails with psoriasis frequently have tiny pits in them. Nails may loosen, thicken, or crumble, and are difficult to treat
- Inverse psoriasis occurs in the armpit, under the breasts, and in skin folds around the groin, buttocks, and genitals
- Guttate psoriasis usually affects children and young adults. It often starts after a sore throat with many small, red, scaly spots appearing on the skin. It frequently clears up by itself in weeks or a few months
- Up to 30% of people with psoriasis may have symptoms of arthritis and 5-10% may have some functional disability from arthritis of various joints. In some people, the arthritis is worse when the skin is very involved. Sometimes the arthritis improves when the condition of the patient’s skin improves
How is psoriasis diagnosed?
Dermatologists diagnose psoriasis by examining the skin, nails, and scalp. If the diagnosis is in doubt, a skin biopsy may be helpful.
To learn more about psoriasis and treatment options, go to www.aad.org