psoriasis occurs in men and women and can occur for the first time at any age.
Q. What is the underlying abnormality?
A. Psoriasis is now considered to be an immunological disease where the body is reacting to an as yet unidentified agent. The result is a change in the skin, where the skin cells, called keratinocytes, start to divide too quickly and mature too slowly. This leads to thickening of the skin and the accumulation of silvery scaling on the skin caused by the immature skin cells on the surface of the skin. Deep in the skin, blood vessels become larger and special blood cells accumulate in the skin. This gives the psoriasis areas their characteristic red colour.
Q. Psoriasis can run in families - how likely are children and siblings to develop the condition?
A. Although a genetic disease, psoriasis is heavily influenced by the environment the person grows up and lives in. One individual may carry the tendency but never express the disease but could pass it onto children who could express it. The risk of passing the tendency onto a child is about 50:50 but the number of children who would actually suffer from psoriasis is much lower.
Q. What makes the condition worse and what makes it better - I'm thinking here of conditions such as pregnancy, drugs and exposure to sunlight?
A. Psoriasis tends to fluctuate in its intensity and then settles at a particular level. In some people this is very minor, only affecting the knees or elbows. In others it is more severe, covering 40 to 60% of the body. Psoriasis will tend to improve in most patients in sunlight and we often use artificial sunlight to treat patients with psoriasis. Some patients get worse in the sun.
Infections such as cold, flu and sore throats can make psoriasis worse and may induce a guttate episode, where multiple small areas of psoriasis occur on the body. 25% of sufferers will develop psoriasis at sites that they have injured - cut, scratched or burnt, a phenomenon called Koebnerisation. Psoriasis may improve or worsen during pregnancy. If it improved during pregnancy it may become much worse after pregnancy.
A number of drugs can make psoriasis worse - lithium used in depression and aspirin. Psoriasis may settle quickly when taking steroids tablets but if the steroids are stopped suddenly, the psoriasis may flare up very badly.
Diet plays little part in psoriasis but fish oil in large quantities has been shown to have a beneficial effect. Stress is a major cause of worsening of psoriasis. In trial, stress management has been shown to improve psoriasis.
Q. Psoriasis can present in a number of different ways - could you explain these and do they have different treatments and outcome?
A. Most patients have plaque psoriasis where the psoriasis appears as well demarcated areas of thickened skin which have a silvery scaling surface. The scale may be fine and grainy or may be very thick. Areas covering 20% of the body may be present.
Some patients develop guttate psoriasis - guttate means raindrop and the psoriasis is present in a raindrop pattern. A few to hundreds of areas may be present. This form is commonest in children or after a sore throat.
Psoriasis in the nails can cause thimble pitting of the nails, accumulation of chalky scale under the nails or cause the nails to become detached from the nail bed.
Psoriasis in the scalp is similar to psoriasis on the body but scaling is very variable and the plaques are hidden by the hair so the sufferer usually complains of scaling and lumps in the scalp.
Erythrodermic psoriasis is where the whole body is red and has fine scaling over the surface. This is a serious event as the body loses heat and fluid from the skin and is more open to infection. Usually this occurs when treatment for psoriasis, particularly tablet treatment, is suddenly withdrawn.
Pustular psoriasis is where the areas of psoriasis are studded with small pustules. This, like erythrodermic psoriasis is a serious condition and can arise because of sudden withdrawal of treatment or can be caused by certain treatments.
Q. Is psoriasis best managed by GP's or should all patients see a dermatologist? At what stage should you advise referral?
A. The vast majority of patients with psoriasis can be treated by the GP with creams and lotions. The most useful are based on vitamin D but preparations containing tar and dithranol have their place. Only 10% of patients require forms of sunlight treatment, treatment in the hospital setting or tablet treatment, which needs to be supervised by a Dermatologist.
Q. What is the link between psoriasis and arthritis and are there any other complications associated with the condition?
A. 25% of psoriasis sufferers develop a form of arthritis. Tests for rheumatoid arthritis are negative but the arthritis can look like rheumatoid arthritis. There is no correlation between the extent or severity of the psoriasis and the severity of the arthritis. The arthritis can be mild or can rapidly progress with destruction of the joints to a crippling disease.
Erythrodermic and widespread pustular psoriasis should be considered to be medical emergencies. There are no other association between psoriasis and other diseases.
Q. What do you regard as the biggest breakthrough in psoriasis treatment?
A. The biggest breakthrough in psoriasis treatment in the last 10 years has been the development of the vitamin D analogues. These are creams that are used once (Tacalcitol) or twice (Calcipotriol) daily. The vitamin D works by slowing down the rate of growth of the skin cells, increasing their rate of maturation and also modify the immune response that is causing the disease.
As long as they are used as directed, they are very safe and effective. Not everyone responds to them but most have good responses.
Q. What is the role of steroid creams in psoriasis?
A. Worldwide, steroid creams of the most frequently used treatment for psoriasis. They do help to settle redness and scaling of the areas and work quickly. After a short time, however, the skin gets used to them and stops responding. Also, the stronger steroids can cause thinning of the skin, stretch mark formation and easy bruising of the skin.
Topical steroids should not, as a general rule, be used as the only therapy in psoriasis. If patients are not responding to a vitamin D cream, a topical steroid can be added in and this may improve response.
Exceptions to this are psoriasis in certain sites, where topical steroids are indicated. In the scalp and on the palms and soles, steroids are very successful and fairly free of side effects. In skin creases such as the groins, mild topical steroids are used as many other treatments will irritate these areas.
Q. Is there any evidence that supplements and alternative approaches have benefit in psoriasis?
A. There is some evidence that Chinese herbal medicine can be effective in psoriasis - however, these agents are unregulated and there is no good information on their safety. There is some data on the use of Aloe Vera and fish oil supplements in the treatment of psoriasis with good results.
We are grateful to the Psoriasis Association for their help in compiling this section.
