Psoriasis

What is this skin condition?

Psoriasis is a non infectious chronic inflammatory skin condition where the skin becomes red and inflamed and the skin cells grow faster than normal leading to dry scaly skin. Well defined red scaly plaques appear often on the elbows and knees but all body sites can be affected. There are many different types of psoriasis including:-

1. Chronic plaque psoriasis- the most common type with well-defined large red scaly plaques
2. Guttate psoriasis – rapid appearance of small drop like plaques following a sore throat
3. Scalp psoriasis- which can occur as an isolated problem
4. Flexural psoriasis – psoriasis involving the skin folds such as the groin and armpits.

Up to 40% of patients can also develop associated psoriatic arthritis. Some patients with very severe psoriasis may have an increased risk of other diseases such as heart attacks and strokes since  the widespread inflammation can have internal effects as well as within the skin.

Why have I got it?

There are over 30 different genes that have been linked to psoriasis. Affected patients have variations in these genes which affect the function of the proteins that produced  by the genes. The genes are involved in functions such as

1. The immune system
2. Skin cell growth
3. Blood vessel growth

The gene variations lead to an increased activity of certain parts of the immune system and an increased chance of over reacting to a trigger. Well known triggers for psoriasis include sore throats, stress and certain drugs. An emerging theory is that in psoriasis the immune system over reacts to the body’s own normal bacteria. We are all covered in bacteria and we need these bacteria to be healthy. One theory for psoriasis is that following an episode of immune activation the immune system remains persistently activated due to a response to normal skin bacteria. This called dysbiosis.  This process has been shown to occur in the gut in the inflammatory bowl disease called Crohn disease.  Further research is needed to confirm whether or not the same thing happens in psoriasis. This over sensitivity to normal bacteria would explain why psoriasis can become a chronic problem.  It would also explain why flexural and scalp psoriasis occur. The skin folds and the hair bearing scalp are areas that are prone to having more resident skin bacteria and fungi.  Flexural psoriasis responds well to Trimovate cream® which as well as an anti-inflammatory steroid contains antifungal and anti-bacterial medicines.

Other variations in genes controlling skin cell growth and blood vessel growth contribute to the development of the red scaly plaques.

It remains unclear why psoriasis occurs where it does. The most common sites are the extensor surfaces- the knees and elbows. One theory as to why these sites are affected suggests an over-reaction or increased susceptibility to skin damage or micro-tearing. Micro tears are microscopic areas of damage in tissues. They can occur in any tissues where there is movement such as the skin and joints. Following a tissue injury an immune response occurs and repair systems are activated. The theory is that patients with psoriasis have an overactive response to micro-tears with an increased number of immune cells moving to affected areas. This would explain why psoriasis is so common on the knees and elbows which move more than most areas of the body.

Regardless of the precise molecular changes that underlie psoriasis, in many people, once the disease starts it often goes on to be a chronic problem. This can clearly be very frustrating. Due to the genetic contribution psoriasis cannot be cured. It can however normally be controlled. There are many different treatments and affected patients generally work their way through the options. Treatment choices are determined by many factors including psoriasis type, time available to apply creams or visit the hospital, other medical conditions and attitude towards potential side effects.

Comparing the treatment options

Self-treatment

The internet is full of many adverts for ‘amazing’ psoriasis treatments. All of the treatments that work well have been investigated by pharmaceutical firms and are prescribed by Doctors. Simple moisturising is benefical in psoriasis and the intensive use of any cream may have some benefit. Be very careful about spending lots of money on products with big promises.

Home based light treatment. Some patients get hold of home based UV light treatments or start to visit sun-tanning salons to try and help their psoriasis. This is NOT recommended. Ultraviolet light treatment , in the form of UVB, does work for psoriasis. However, UVB is the wavelength that causes sunburn. When patients receive UVB at a Dermatology Centre they are given carefully measured doses. Also, as the treatments progress the skin becomes more tolerant of the UVB and the doses need to be increased to maintain the therapeutic effect. Home based UV devices will have not be powerful enough to deliver a true benefit and could be harmful.

Sun-tanning machines are simply terrible and may well be banned at some stage. There is an epidemic of skin cancer in pale skinned people of Northern European origin. All departments are seeing patients who have developed skin cancer as a consequence of excessive sunbed use.  The damage to the skin is especially bad with long term weekly treatments or following burning episodes. Sunbeds are now in the same United Nations carcinogen category as cigarettes.

Alcohol triggers inflammation in the body and this includes the skin.  Alcohol makes psoriasis worse and should be avoided as much as possible.

Creams

1. Moisturising creams (emollients). Moisturising the skin is helpful for nearly all inflammatory conditions. If the skin is dry it will often be more prone to inflammation. There are many moisturising options to choose from. Link to products.
2. Coal tar creams. These have been used for decades to treat psoriasis . Some of the milder ones area available over the counter such as exorex lotion.
3. Most other psoriasis creams require a prescription and a visit to the GP

Scalp treatments

There is a long list of products for scalp psoriasis. There are two components to treating scalp psoriasis, the first is to remove the skin scales that have built up and the second is to reduce the inflammation. Moisturising products help as increasing the water content in the top layer of dead dry skin cells weakens the bonds between the cells and enables removal. Other products contain salicylic acid which dissolves the dead skin cells. Once the scale is removed the inflammation can be treated. Coal tar based products are often helpful. Many can bought over the counter but others need a prescription. Topical steroid and vitamin D based products can help and need a prescription.

Life style

A higher proportion of psoriasis patients develop problems such as obesity and diabetes. It remains unclear which comes first. Increasingly it is felt that obesity can be a trigger for psoriasis so trying to maintain a healthy weight is an important part of treating psoriasis.

Alcohol is increasingly recognised as a trigger for inflammation in many organs. Alcohol induced liver inflammation triggers thickening called fibrosis which can lead to cirrhosis. Increasingly alcohol is felt to be a trigger for skin inflammation and should be avoided as much as possible.

Help from your GP

Creams

Many of the over the counter creams will also be available from your GP. Other prescribed products to try include

1. Dovonex ointment- a vitamin D analogue , good at reducing scaling but does not always clear the redness
2. Topical steroids- helpful in small quantities. Long term use of stronger steroids  can thin the skin. Psoriasis usually becomes resistant to steroids with long term use
3. Dovobet-  gel or foam ( Enstilar) - a combination of dovonex and betnovate. Often helpful but should be used in short bursts one  week on, one  week off to prevent resistance building up
4. Tar products. Some coal tar products use refined tars whciha re not too smelly eg exorex. Products containing stronger tar are often a bit smelly but can be more effective eg psoridem. Approximately 30% of patients have a good response to tar and if tolerated it can be a good long term treatment.
5. Tazorotene gel is licensed for psoriasis but only works in a small proportion of people.

Scalp treatments

Options include

1. Tar based products such as sebco or tar pomade
2. Vitamin D lotions such as dovonex scalp application
3. Topical steroids such as betnovate scalp application

 

Help from a Dermatologist

If the normal creams are not working it is time to find a good Dermatologist . They will be able to  discuss second , third and fourth line treatment options.

Second line.

For most patients this is some form of phototherapy.

Third line.

Various tablet and injection based treatments are widely available (these are called systemic drugs as they have an effect on the whole body and not just the skin) . The most common systemic drugs are methotrexate and acitretin. Ciclosporin is also sometimes used. Follow the links to the BAD website for further information on these drugs.

Fourth line.

In the last 10 years there has been an explosion in the number of new drugs available to treat psoriasis. These are mainly injectable drugs and are called biologics as they are produced in living biological cell cultures. Most of them are antibodies which bind to proteins which are involved in causing psoriasis. They all work by suppressing the overactive immune cells that are a key cause of psoriatic inflammation. To get a sustainned response you need to keep using the medication. There are now more than 10 biologic drugs for psoriasis. Some, such as adalimumab have been in use for almost 15 years. The safety record is very good for all of the biologic drugs.

There are also some new small molecule drugs for psoriasis such as apremilast. The benefits tend to be less than the biologics.

Your Dermatologist will be able to explain if you are eligible or not.  You will usually have had to try at least one standard systemic medication and have a psoriasis severity score ( PASI)  of over 10. They will also explain the potential side effects.