Psoriasis is a common skin disorder and one of the most baffling and persistent. Underlying skin cells on the knees, elbows and scalp of sufferers multiply up to 10 times faster than normal; as they pile up on the surface, they cause raised, white-scaled patches. The reason for the rapid cell growth is unknown, but outbreaks are triggered by the immune system.
Although not contagious, psoriasis tends to run in families. It is undoubtedly a complex genetic disease. People from European descent are particularly susceptible, especially those with a blood relative who suffers from the disorder.
Advertisement
Although psoriasis may be stressful and embarrassing, most outbreaks are relatively benign – early treatment of the plaques will help prevent symptoms becoming more severe, and plaques generally disappear within weeks. Psoriasis occur in different forms:
In Guttate psoriasis, small droplike, scaly areas appear on the torso, limbs and scalp. Guttate psoriasis is usually triggered by viral respiratory infections or certain bacterial (streptococcal) infections.
In another uncommon form of psoriasis, pustular psoriasis, large and small blisters of non-infectious pus (pustules) form on the palms of the hands and soles of the feet, and sometimes over the entire body.
Very rarely, psoriasis covers the entire body and produces exfoliative erythrodermic psoriasis, in which the entire skin becomes inflamed. This form of psoriasis is serious because, like a burn, it keeps the skin from serving as a protective barrier against injury and infection. The patient loses heat and can go into cardiac failure, as it can cause a "high output" state.
About 7% of people with psoriasis also have joint inflammation that produces symptoms of arthritis. This condition is called psoriatic arthritis.
What causes psoriasis?
Recent research indicates that psoriasis is a disorder of the immune system. A type of white blood cell, called a T cell, helps protect the body against infection and disease. It seems that abnormalities in the so-called T helper cells are associated with psoriasis. It is what precipitates the change that is the mystery.
An episode of psoriasis may result from a number of factors. Emotional stress is one – many patients suffering a flare-up, report a recent emotional stressor, such as a new job or the death of a loved one. Severe sunburn, obesity and certain drugs – including the anti-malaria medication chloroquine, lithium, anti-depressant beta-blockers like propranolol and metoprolol, medication taken to treat high blood pressure, and almost any medicated ointment or cream – can aggravate psoriasis. Streptococcal infections (especially in children), and injured skin (bruises and scratches) can also stimulate the formation of new plaques. Alcohol consumption clearly makes psoriasis worse.
What are the symptoms?
Psoriasis usually starts as one or more small psoriatic plaques – dark-pink, raised patches of skin with white flaky scales – usually on the scalp, knees, elbows, back and buttocks. Sometimes the eyebrows, armpits, navel and groin may also be affected. Usually, psoriasis produces only flaking. Even itching is uncommon. On the scalp, flaking may be mistaken for severe dandruff, but the patchy nature of psoriasis, with flaking areas interspersed among completely normal ones, distinguishes the disease from dandruff. Although the first plaques may clear up by themselves, others may soon follow. Some plaques may remain thumbnail-sized, but in severe cases, psoriasis may spread to cover large areas of the body, sometimes in striking ring-shaped or spiral patterns.
When flaking areas heal, the skin looks completely normal and hair growth is unchanged. Most people with limited psoriasis suffer few problems beyond the flaking, although the skin’s appearance may be embarrassing.
Psoriasis can also break out around and under fingernails and toenails, pitting, discolouring and thickening them, and sometimes even separating them from underlying tissue.
When to see a doctor
If your psoriasis becomes worse after you stop taking heavy doses of corticosteroid for this or another ailment, you may need a different course of medical treatment.
If your skin inflammation does not respond to any form of treatment; you need to be checked for the possibility of a more serious underlying ailment.
Diagnosis
Psoriasis may be misdiagnosed at first because many other disorders can produce similar plaques and flaking. As psoriasis develops, the characteristic scaling pattern is usually easy for doctors to recognise, so diagnostic tests usually aren’t needed. However, to confirm a diagnosis, a doctor may perform a skin biopsy (removal of a skin specimen and examination under a microscope). This is not usually necessary.
Treatment
Psoriasis is treated according to the severity of the disease and its responsiveness to initial treatments:
Topical treatment
Phototherapy
Systemic treatment
Topical treatment
The first stage of treatment is topical (medicines are applied to the skin). When a person has only a few small plaques, psoriasis generally responds quickly. A soak in a warm bath for 10 to 15 minutes, followed immediately by application of an ointment or cream (emollient) that lubricates the skin (petroleum jelly is a good example) may relieve symptoms for a short while. Applying an emollient once or twice a day helps your skin retain moisture. Some doctors recommend salicylic acid ointment, which smoothes the skin by promoting the shedding of psoriatic scales.
Ointments containing corticosteroids are effective, and can be made more effective if the area is wrapped in cellophane after applying them. However, because they can have harmful side effects, you should be careful not to overuse them. This may thin the skin and lose its efficacy.
Coal-tar ointments and shampoos can alleviate symptoms, but many psoriasis patients seem vulnerable to the side effects – in particular folliculitis, a pimple-like rash affecting the hair follicles.
A new medication, calcipotriol, is a synthetic form of Vitamin D3 (this is not the same as Vitamin D supplements). It controls the excessive production of skin cells, and can help those who can’t tolerate some of the other creams. It works best in conjunction with phototherapy.
Anthralin therapy is usually reserved for severe forms of psoriasis. Anthralin salve is carefully applied to the affected areas and removed after 30 to 60 minutes. All the white scales should be gone, revealing an underlying layer of fresh, normal skin. However, if not properly applied by a trained therapist, anthralin can irritate healthy skin and leave stains that can last several weeks. It is therefore not commonly used anymore except in dermatological hospital treatment.
Tazarotene (a new topical Vit A derivative or retinoid), is very useful for plaque and scalp psoriasis. It is applied at night. It may be irritant and the current use of emollients is recommended. It is particularly good when a corticosteroid is applied in the morning. The steroid prevents irritation and the retinoid prevents thinning of the skin.
Phototherapy
Exposure to ultraviolet light, for example during the summer months, may help exposed regions of affected skin clear up spontaneously. Sunbathing often helps to clear up the plaques on larger areas of the body. For persistent, difficult-to-treat cases of psoriasis, ultraviolet (UV) light therapy may be prescribed; and is often extremely successful.
UVB phototherapy is used to treat widespread psoriasis and lesions that resist topical treatment. A light panel or light box is used, either at the doctor’s surgery or at home. Sometimes it is combined with topical treatments, for example by applying a coal tar ointment before therapy; or with calcipotriol or tazarotine
The PUVA treatment (UVA phototherapy) is recommended for extensive psoriasis where more than 10% of the skin is affected, or when rapid clearing is required because the disease interferes with a patient’s occupation. It combines oral or topical administration of a medicine called psoralen with exposure to ultraviolet A (UVA) light. Psoralen makes the skin extra sensitive to the effects of ultraviolet light.
PUVA treatment may clear up the skin for several months. However, possible side effects including nausea, headache, fatigue, burning and itching. Generally, researchers have found that PUVA is effective and relatively safe. However, when combined with oral medications such as methotrexate or cyclosporine, it can increase the risk of skin cancer, even decades after treatment has been discontinued.
Systemic therapy
For more severe forms of psoriasis, a doctor may prescribe internal medications such as methotrexate. Used to treat some forms of cancer, this drug interferes with the growth and multiplication of skin cells and suppresses the immune system. It can be effective in extreme cases but may cause liver damage or decrease the production of oxygen-carrying red cells, infection-fighting white blood cells and clot-enhancing platelets. Other effective medications, such as retinoids, cyclosporine and hydroxyurea may also have serious side effects and none of these should be taken by pregnant women or women planning to get pregnant.
The most effective medication for treating pustular psoriasis is etretinate. It can cause birth defects and is not recommended for women of child-bearing age.
Prevention
People who have a genetic predisposition to psoriasis should try to avoid psoriasis triggers, such as skin injuries, insect bites, viral or bacterial infections, sunburn, stress, alcohol and being overweight. Any form of stress (emotioinal, physical or infective) can trigger psoriasis.
Reviewed by Dr Leonore R.J. van Rensburg, MBChB (UCT), M. Med. Dermatology (US).
Bookmark with:
What are social bookmarks?