Psorias is a non-contagious skin condition that produces red, dry plaques of thickened skin. The dry flakes and skin scales are thought to result from the rapid proliferation of skin cells that is triggered by abnormal lymphocytes from the blood. Psoriasis commonly affects the skin of the elbows, knees, and scalp.
Some people have such mild psoriasis (small, faint dry skin patches) that they may not even suspect that they have a medical skin condition. Others have very severe psoriasis where virtually their entire body is fully covered with thick, red, scaly skin.
What causes psoriasis?
The exact cause remains unknown. There may be a combination of factors, including genetic predisposition and environmental factors. It is common for psoriasis to be found in members of the same family. The immune system is thought to play a major role. Despite research over the past 30 years looking at many triggers, the "master switch" that turns on psoriasis is still a mystery
Psoriasis typically looks like red or pink areas of thickened, raised, and dry skin. It classically affects areas over the elbows, knees, and scalp. Essentially any body area may be involved. It tends to be more common in areas of trauma, repeat rubbing, use, or abrasions.
Psoriasis has many different appearances. It may be small flattened bumps, large thick plaques of raised skin, red patches, and pink mildly dry skin to big flakes of dry skin that flake off.
There are several different types of psoriasis, including psoriasis vulgaris (common type), guttate psoriasis (small, drop like spots), inverse psoriasis (in the folds like of the underarms, navel, and buttocks), and pustular psoriasis (pus-filled, yellowish, small blisters). When the palms and the soles are involved, this is known as palmoplantar psoriasis.
Sometimes pulling of one of these small dry white flakes of skin causes a tiny blood spot on the skin. This is medically referred to as a special diagnostic sign in psoriasis called the Auspitz sign.
Genital lesions, especially on the head of the penis, are common. Psoriasis in moist areas like the navel or area between the buttocks (intergluteal folds) may look like flat red patches. These atypical appearances may be confused with other skin conditions like fungal infections, yeast infections, skin irritation, or bacterial Staph infections.
On the nails, it can look like very small pits (pinpoint depressions or white spots on the nail) or as larger yellowish-brown separations of the nail bed called "oil spots." Nail psoriasis may be confused with and incorrectly diagnosed as a fungal nail infection.
On the scalp, it may look like severe dandruff with dry flakes and red areas of skin. It may be difficult to tell the difference between scalp psoriasis and seborrhea (dandruff). However, the treatment is often very similar for both conditions.
Genetic Causes of Psoriasis
Researchers have found 9 gene mutations that may be involved in causing psoriasis. One of these mutations on chromosome 6, called PSORS-1, appears to be a major factor that can lead to psoriasis. Mutations on genes cause certain cells to function differently. With psoriasis, these mutations seem to largely affect T-helper cells.
Immune System Causes of Psoriasis
In a normally functioning immune system, white blood cells produce antibodies to foreign invaders such as bacteria and viruses. These white blood cells also produce chemicals that aid in healing and fighting infective agents. But with psoriasis, special white blood cells called T-cells become overactive.
These T-cells "attack" the skin and set off a cascade of events that make the skin cells multiply so fast they start to stack up on the surface of the skin. Normal skin cells form, mature, then are sloughed off every 30 days. But in plaque psoriasis the skin goes through this whole process in 3-6 days.
Normally T-cells produce chemicals that help heal the skin. In psoriasis, T-cells produce an abnormally large amount of these chemicals and actually cause more inflammation in the skin and joints.
Environmental Causes of Psoriasis
Not everyone who has these gene mutations gets psoriasis and there are several forms of psoriasis that people can develop. Certain environmental triggers play a role in causing psoriasis in people who have these gene mutations. Learn more about other psoriasis triggers.
How is psoriasis diagnosed?
The diagnosis of psoriatic arthritis is typically made by a physician examination, medical history, and relevant family history. Sometimes, lab tests and X-rays may be used to determine the severity of the disease and to exclude other diagnoses like rheumatoid arthritis and osteoarthritis.
What is the treatment for psoriasis?
There are many effective treatment choices for psoriasis. The best treatment is individually determined by the treating physician and depends, in part, on the type of disease, the severity, and the total body area involved.
For mild disease that involves only small areas of the body (like less than 10% of the total skin surface), topical (skin applied) creams, lotions, and sprays may be very effective and safe to use. Occasionally, a small local injection of steroids directly into a tough or resistant isolated psoriasis plaque may be helpful.
For moderate to severe disease that involves much larger areas of the body (like 20% or more of the total skin surface), topical products may not be effective or practical to apply. These cases may require ultra-violet light treatments or systemic (total body treatments such as pills or injections) medications. Internal medications usually have greater risks.
For psoriatic arthritis, systemic medications are generally required to stop the progression of permanent joint destruction. Topical therapies are not effective.
It is important to keep in mind that as with any medical condition, all medications carry possible side effects. No medication is 100% effective for everyone, and no medication is 100% safe. The decision to use any medication requires thorough consideration and discussion with your physician. The risks and potential benefit of medications have to be considered for each type of psoriasis and the individual patient. Some patients are not bothered at all by their skin symptoms and may not want any treatment. Other patients are bothered by even small patches of psoriasis and want to keep their skin clear. Everyone is different and, therefore, treatment choices also vary depending on the patient's goals and expressed wishes.
An approach to minimize the toxicity of some of these medicines has been commonly called "rotational" therapy. The idea is to change the antipsoriasis drug every six to 24 months in order to minimize the possible side effects from any one type of therapy or medication.
In another example, a patient who has been using strong topical steroids over large areas of their body for prolonged periods may benefit from stopping the steroids for a while and rotating onto a different therapy like calcitriol (Vectical), light therapy, or an injectable biologic.