Psoriasis is a chronic, recurring disease that causes one or more raised, red patches that have silvery scales and a distinct border between the patch and normal skin.
A problem with the immune system may play a role, and some people are genetically predisposed to psoriasis.
Characteristic scales or red patches can appear anywhere on the body in large or small patches, particularly the elbows, knees, and scalp.
This disease is treated with a combination of medications applied to the skin, exposure to ultraviolet light (phototherapy), and medications taken by mouth or given by injection.
Psoriasis is common and varies widely among different populations worldwide. It is likely that psoriasis is underreported among people with dark skin compared with people with light skin.
Psoriasis begins most often in people aged 16 to 22 years and aged 57 to 60 years. However, all people of all ages are susceptible.
The patches of psoriasis occur because of an abnormally high rate of growth of skin cells. The reason for the rapid cell growth is unknown, but a problem with the immune system is thought to play a role. The disorder often runs in families, and certain genes are associated with psoriasis.
Some well-identified triggers of psoriasis include
Minor skin injuries
Sunburn
HIV infection
Streptococcal infection, such as strep throat (leading to guttate psoriasis)
Emotional stress
Alcohol consumption
Tobacco smoking
Obesity
Symptoms of Psoriasis
Image provided by Thomas Habif, MD.
Image courtesy of Karen McKoy, MD.
Plaque psoriasis, the most common type of psoriasis, usually starts as one or more small red, silvery, shiny patches (plaques) on the scalp, elbows, knees, back, or buttocks. The eyebrows, underarms, navel, the skin around the anus, and the cleft where the buttocks meet the lower back may also be affected. Many people with psoriasis may also have deformed, thickened, and pitted nails.
The first patches may clear up after a few months or remain, sometimes growing together to form larger patches. Some people never have more than one or two small patches, and others have patches covering large areas of the body. Thick patches or patches on the palms of the hands, soles of the feet, or skinfolds of the genitals are more likely to itch or hurt, but many times the person has no symptoms. Although the patches do not cause extreme physical discomfort, they are very obvious and often embarrassing to the person. The psychologic distress caused by psoriasis can be severe.
Psoriasis persists throughout life but may come and go. Symptoms of psoriasis are often diminished during the summer when the skin is exposed to bright sunlight. Some people may go for years between occurrences.
About 5 to 30% of people with psoriasis develop arthritis (psoriatic arthritis). Psoriatic arthritis causes joint pain and swelling.
Flare-ups
Psoriasis may flare up for no apparent reason or as a result of a variety of circumstances. Flare-ups often result from conditions that irritate the skin, such as minor injuries and severe sunburn. Sometimes flare-ups occur after infections, such as colds and strep throatobese, infected with the human immunodeficiency virus (HIV), or smoke tobacco.
Uncommon types of psoriasis
Some uncommon types of psoriasis can have more serious effects.
Erythrodermic psoriasis causes all of the skin on the body to become red and scaly. This form of psoriasis is serious because, like a burn, it keeps the skin from serving as a protective barrier against injury and infection.
Pustular psoriasis is another uncommon form of psoriasis. In this form, large and small pus-filled blisters (pustules) are scattered widely on the body.
Palmoplantar psoriasis is a form of pustular psoriasis in which pustules occur primarily on the hands and feet. It is sometimes called palmoplantar psoriasis of the palms and soles.
Guttate psoriasis is an uncommon form of psoriasis in which multiple, small patches (plaques) appear suddenly, usually on the trunk in children and young adults after a strep throat infection. Antibiotics to treat the strep infection make the patches go away in some people, but others still need additional therapies.
Diagnosis of Psoriasis
A doctor's evaluation
Sometimes skin biopsy
Doctors base the diagnosis of psoriasis on how the scales and plaques look and where they appear on the body.
Sometimes, doctors take a sample of skin tissue and examine it under a microscope to rule out other disorders (such as skin cancer).
Treatment of Psoriasis
Topical treatments
Phototherapy
Systemic treatments
Many medications are available to treat psoriasis. Most often, a combination of medications is used, depending on the severity and extent of the person's symptoms.
Topical treatments
Topical treatments are applied to the skin. They are the most common treatments for psoriasis. Nearly everyone with psoriasis benefits from skin moisturizers (emollients).
Other topical agents include corticosteroids
Many of these treatments are irritating to the skin, and doctors must find which ones work best for each person.
Phototherapy
Phototherapy (exposure to ultraviolet light) also can help clear up psoriasis for several months at a time (see sidebar Phototherapy: Using Ultraviolet Light to Treat Skin Disorders). Phototherapy is often used in combination with various topical medications, particularly when large areas of skin are involved, but it is not being used as much because other effective medications are available. Traditionally, treatment has been with phototherapy combined with the use of psoralens (medications that make the skin more sensitive to the effects of ultraviolet light). This treatment is called PUVA (psoralen plus ultraviolet A).
Many doctors are now using narrowband ultraviolet B (NBUVB) treatments, which are as effective as PUVA. However, NBUVB treatments are done without psoralens and therefore do not have the same side effects, such as extreme sensitivity to sunlight.
Doctors can also treat specific patches of the skin directly by using a laser that focuses ultraviolet light (called excimer laser therapy).
Phototherapy: Using Ultraviolet Light to Treat Skin Disorders
Exposure to sunlight is helpful for certain skin disorders. One component of sunlight―ultraviolet (UV) light―is responsible for this effect. UV light has many different effects on skin cells, including altering the amounts and kinds of chemicals they make and causing the death of certain cells that can be involved in skin diseases. The use of UV light to treat disease is called phototherapy. Psoriasis and atopic dermatitis are the disorders most commonly treated with phototherapy. Because exposure to natural sunlight varies in intensity and is not practical for a large part of the year in certain climates, phototherapy is nearly always done with artificial UV light. Treatments are given in a doctor's office or in a specialized treatment center. UV light, which is invisible to the human eye, is classified as A, B, or C, depending on its wavelength. Ultraviolet A (UVA) penetrates deeper into the skin than ultraviolet B (UVB). UVA or UVB is chosen based on the type and severity of the person's disorder. Ultraviolet C is not used in phototherapy. Some lights produce only certain specific wavelengths of UVA or UVB (narrowband therapy), which are used to treat specific disorders. Narrowband therapy helps limit the sunburn–like effect caused by phototherapy. Phototherapy is sometimes combined with the use of a psoralen. The combination of a psoralen plus UVA is known as PUVA therapy. Psoralens are medications that may be taken by mouth before treatment with UV light. Psoralens sensitize the skin to the effects of UV light, allowing shorter, less intense exposure. Side effects of phototherapy include pain and reddening similar to sunburn with prolonged exposure to UV light. UV light exposure also increases the long-term risk of skin cancer, but the risk is small for brief courses of treatment. Psoralens often cause nausea and extreme sensitivity to sunlight. In addition, because psoralens enter the lens of the eye, UV-resistant sunglasses must be worn for at least 12 hours after undergoing PUVA therapy. |
Systemic treatments
Systemic treatments are medications that affect the whole body or certain systems of the body. They can be taken by mouth or injected.
Systemic immunosuppressants are medications that intentionally weaken (suppress) the immune system to keep it from making psoriasis worse. Immunosuppressants can reduce the body's ability to fight infections. Examples include
can be used to treat severe psoriasis. This medication may cause high blood pressure and damage the kidneys.
commonly causes gastrointestinal problems and bone marrow suppression (decreased production of red blood cells, white blood cells, and platelets). It may also increase the risk of lymphoma and other cancers.
Biologic agents
Other medications may be given to treat moderate to severe forms of psoriasis and psoriatic arthritis:
Systemic retinoids,isotretinoin is often preferred), and palmoplantar psoriasis. These medications are given by mouth. They can cause severe birth defects and should not be taken by women who may become pregnant. Women should wait at least 3 years after their last dose of acitretin and at least 1 month after their last dose of isotretinoin before attempting pregnancy. These medications can raise levels of triglycerides and cause reversible problems with the liver, blood counts, bones, and hair.
is another option and it is taken by mouth. The most common side effects are nausea and diarrhea.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Psoriasis Foundation: A resource providing information about treatments and community support
