Psoriasis is a relatively common skin condition affecting around two per cent of the UK population. It causes thickened flat plaques or patches of skin that are red, crusty, itchy and flaky.This information sheet from Great Ormond Street Hospital (GOSH) explains the causes, symptoms and treatment of psoriasis and where to get help.

The appearance of the plaques can lead to unwanted attention but it is not infectious so it cannot be passed on from person to person. Psoriasis is a long term condition but many people find their symptoms come and go as they grow older.

What causes psoriasis?

Normally, our skin regenerates every few weeks, with new skin cells forming deep inside the body and gradually working their way towards the surface to replace dead skin cells that flake off naturally. In psoriasis, this cycle of regeneration is greatly speeded up so that immature new cells reach the surface and dead skin cells build up on the surface of the skin. This leads to the characteristic plaques or patches of thickened skin.

Various things have been identified as a trigger for a worsening of symptoms or development of new plaques including stress, injury, some medications and a particular throat infection called strep throat. Psoriasis is thought to be an autoimmune condition, where the immune system attacks healthy skin cells instead of foreign invaders such as bacteria and viruses as it should. It can also run in families although the precise genetic basis for the condition has not yet been identified.

What are the signs and symptoms of psoriasis?

The main symptom of psoriasis is the development of raised plaques or patches of skin that are red, crusty, itchy and flaky. Plaques can develop on any part of the body and will vary in size from person to person and over time as well. Sometimes the thickened areas of skin can crack and bleed, particularly if they are scratched or over a flexible area such as a joint, which leaves the skin open to infection.

As well as affecting the skin, psoriasis can affect the finger and toe nails too, leaving them with an uneven pitted surface and growing thicker over time. Psoriasis can also affect the joints causing swelling and soreness – this is referred to as psoriatic arthritis.

How is psoriasis diagnosed?

As psoriasis is such a common condition, it can often diagnosed by the family doctor (GP) or health visitor. They will ask about when the symptoms appeared, how long they have been present and how they are affecting a child’s everyday life. They will also look at the child’s skin to ‘map’ which areas are affected.

If any patches seem to be infected, that is, they are oozing and/or crusty, they may take a skin swab to send to the laboratory for testing. This is needed to identify the bug causing the infection.

If the psoriasis is very severe or there is any doubt about the diagnosis, a referral to a dermatologist (specialist skin doctor) may be suggested. Very rarely, they may request a skin biopsy – small sample of skin – for examination under a microscope, to confirm or rule out the diagnosis. If the joints are affected, a referral to a rheumatologist (specialist joint doctor) may also be needed.

How is psoriasis treated?

Although there is no cure for psoriasis, there are many options for improving the symptoms. Topical treatments applied directly to the affected patches of skin include steroid and vitamin D creams. Coal tar is a treatment that has been used for decades and works well, but is a bit smelly and messy so some people are reluctant to use it.

Phototherapy with ultraviolet light can also improve the skin plaques – this is delivered at specialist centres rather than at GP surgeries. For severe and extensive psoriasis systemic medicines may be needed. These are medicines that treat the entire body, not just the affected plaques. These medicines can have side effects so are prescribed and monitored by a specialist centre.

Some people find it hard to cope with any unwanted attention to their skin problems, particularly if they are on an area of exposed skin such as the hands or face. Psychological support to develop coping strategies can be invaluable, as can meeting other people with the same condition to learn from their experience.

What happens next?

Psoriasis is a long term condition but the symptoms can come and go throughout life. It can be helpful to recognise any triggers and work to avoid them. There are plenty of treatment options so there is bound to be one that suits the child, although various options may need to be tried first.

Compiled by:
The Dermatology department in collaboration with the Child and Family Information Group
Last review date:
August 2016