Psoriasis is a non-contagious common skin condition that causes rapid skin cell reproduction resulting in red, dry patches of thickened skin. The dry flakes and skin scales are thought to result from the rapid buildup of skin cells. 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.
Psoriasis is considered a non-curable, long-term (chronic) skin condition. It has a variable course, periodically improving and worsening. Sometimes psoriasis may clear for years and stay in remission. Some people have worsening of their symptoms in the colder winter months. Many people report improvement in warmer months, climates, or with increased sunlight exposure.
Psoriasis is seen worldwide, in all races, and both sexes. Although psoriasis can be seen in people of any age, from babies to seniors, most commonly patients are first diagnosed in their early adult years.
Patients with more severe psoriasis may have social embarrassment, job stress, emotional distress, and other personal issues because of the appearance of their skin.

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 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 (liquid-filled yellowish small blisters). Additionally, a separate entity affecting primarily the palms and the soles 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.

Doctor can usually diagnose psoriasis after talking to you about your signs and symptoms and examining your skin. Sometimes, however, your doctor may take a small sample of skin (biopsy) that's examined under a microscope to determine the exact type of psoriasis and to rule out other disorders. A skin biopsy is usually done in a doctor's office using a local anesthetic.

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 systemic or total body treatments such as pills, light treatments, or injections. Stronger medications usually have greater associated possible risks.

For psoriatic arthritis, systemic medications that can stop the progression of the disease may be required. Topical therapies are not effective.

Topical (skin applied) medications include topical corticosteroids, vitamin D analogue creams, topical retinoids, moisturizers, topical immunomodulators (tacrolimus and pimecrolimus), coal tar, anthralin, and others.

Topical corticosteroids (steroids, such as hydrocortisone) are very useful and often the first-line treatment for limited or small areas of psoriasis. These come in many preparations, including sprays, liquid, creams, gels, ointments, and mousses. Steroids come in many different strengths, including stronger ones are used for elbows, knees, and tougher skin areas and milder ones for areas like the face, underarms, and groin. These are usually applied once or twice a day to affected skin areas.

Strong steroid preparations should be limited in use. Overuse or prolonged use may cause problems including potential permanent skin thinning and damage called atrophy.

A vitamin D analogue cream called calcipotriene has also been useful in psoriasis. The advantage of calcipotriene is that it is not known to overly thin the skin like topical steroids. It is important to note that this drug is not regular vitamin D and is not the same as taking regular vitamin D or rubbing it on the skin.

Calcipotriene may be used in combination with topical steroids for better results. Results with calcipotriene alone may be slower and less than results achieved with typical topical steroids. Not all patients may respond to calcipotriene as well as to topical steroids.

A special precaution with calcipotriene is that it should not be used on more than 20% of the skin in one person. Overuse may cause absorption of the drug and an abnormal rise in body calcium levels.

Moisturizers, especially with therapeutic concentrations of salicylic acid, lactic acid, urea, and glycolic acid may be helpful in psoriasis. These may be used one to three times a day on the body and do not generally have a risk of problematic skin thinning (atrophy).

Immunomodulators (tacrolimus and pimecrolimus) have also been used with some success in limited types of psoriasis. These have the advantage of not causing skin thinning. They may have other potential side effects, including skin infections and possible malignancies (cancers). The exact association of these immunomodulator creams and cancer is controversial.

Coal tar is available in multiple preparations, including shampoos, bath solutions, and creams. Coal tar may help reduce the appearance and decrease the flakes in psoriasis. The odor, staining, and overall messiness with coal tar may make it harder to use and less desirable than other therapies. A major advantage with tar is lack of skin thinning.

Oral medications include acitretin, cyclosporine, methotrexate, mycophenolate mofetil, and others. Oral prednisone (corticosteroid) is generally not used in psoriasis and may cause a disease flare if administered to many patients.

Acitretin is an oral drug used for certain types of psoriasis. It is not effective in all types of the disease. It may be used in males and females who are not pregnant and not planning to become pregnant for at least three years. The major side effects include dryness of skin and eyes and temporarily elevated levels of triglycerides and cholesterol (fatty substance) in the blood. Blood tests are generally required before starting this therapy and periodically to monitor triglyceride levels. Patients should not become pregnant while on this drug and usually for at least three years after stopping this medication.

Cyclosporine is a potent immunosuppressive drug used for other medical uses, including organ-transplant patients. It may be used for severe, difficult-to-treat cases of widespread psoriasis. Improvement and results may be very rapid in onset. It may be hard to get someone off of cyclosporine without flaring their psoriasis. Because of the potential cumulative toxicity, cyclosporine should not be used for more than one to two years for most psoriasis patients. Major possible side effects include kidney and blood-pressure problems.

Methotrexate is a common drug used for rheumatoid arthritis and, in high doses, for cancer treatment. For psoriasis, it has been used effectively for many years. It is usually given in small weekly doses (5 mg-15 mg). Blood tests are required before and during therapy. The drug may cause liver damage in some patients, particularly if there is preexisting liver disease or if given for prolonged periods of time. Close physician monitoring and monthly to quarterly visits and labs are generally required.

The newest category of psoriasis drugs are called biologics. All biologics modulate (adjust) and sometime suppress (quiet) the immune system that is overactive in psoriasis. Currently available biologic drugs include alefacept (Amevive), adalimubab (Humira), infliximab (Remicade), etanercept (Enbrel), and ustekinumab.

Light therapy is also called phototherapy. There are several types of traditional medical light therapies called PUVA, UVB, and narrow band UVB.

Natural sunlight is also used to treat psoriasis. Daily, short, controlled exposures to natural sunlight may help or clear psoriasis in some patients. Skin unaffected by psoriasis and sensitive areas such as the face and hands may need to be protected during sun exposure.

There are also multiple newer light sources like lasers and photodynamic therapy (use of a light activating medication and a special light source) that have been used to treat psoriasis.

PUVA is a special treatment using a photosensitizing drug and timed artificial-light exposure. The photosensitizing drug in PUVA is called psoralen. These treatments are usually administered in a physician's chamber two to three times per week. Several weeks of PUVA is usually required before seeing significant results. The light exposure time is slowly and gradually increased during each subsequent treatment.

Psoralens may be given orally as a pill or topically as a bath or lotion. After a short incubation period, the skin is exposed to a special wavelength of ultraviolet light called UVA. Patients using PUVA are generally sun sensitive and must avoid sun exposure for a period of time after PUVA.

UVB phototherapy is an artificial light treatment using a special wavelength of light. It is frequently given daily or two to three times per week. UVB is also a component of natural sunlight. UVB dosage is based on time and exposure is gradually increased by 15-60 seconds per treatment or per week. Potential side effects with UVB include skin burning, skin damage, and possible increased risk of skin cancer, including melanoma. The relative increase in skin cancer risk with UVB treatment needs further study.

Complications
Depending on the type and location of the psoriasis and how widespread the disease is, psoriasis can cause complications. These include: