What is psoriasis? A medical overview

Psoriasis is a skin condition which often affects teenagers and young adults, although it can occur at any age. The main symptoms of psoriasis are patches or plaques, which can make the skin dry, itchy and sometimes flake. Hyperpigmentation (when the colour of the skin changes) is sometimes left after psoriasis clears up.
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There are different types of psoriasis, such as plaque psoriasis and guttate psoriasis. The severity of psoriasis is often measured on the basis of how much of the skin is affected, known as the ‘PASI’ (Psoriasis Area Severity Index) score.
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Psoriasis can affect skin anywhere on the body. Some subtypes of psoriasis describe the location of the body affected, such as scalp psoriasis. As well as the skin, psoriasis can affect the nails. There is also a type of arthritis associated with psoriasis and psoriatic arthritis (sometimes shortened to PA or PsA) can make the joints swollen, stiff and painful. Not everyone who has psoriasis will develop psoriatic arthritis and not everyone who has psoriatic arthritis will have the skin condition, but the chances are higher.
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A ‘normal’ skin cycle involves new skin cells being produced, moved through the layers of the skin and flaking off every 3-4 weeks. In psoriasis, this process happens much quicker (only a few days). This means that the skins cells are not fully developed and build up on the surface of the skin. It is not fully known what causes the difference in the pace of the skin cycle, but some research suggests it occurs because some cells and processes in the immune system become over-active. This can cause inflammation (swelling) and scaling on the skin. The triggers for starting psoriasis or a ‘flare-up’ vary from person to person. Some common examples include stress and illness (e.g. the bacterial infection called ‘strep-throat’). A trigger for one person’s psoriasis may not be a trigger for another person’s.
There are different medical treatments available for psoriasis. Some types of treatment can be bought from a shop (‘over-the-counter’). Other treatments must be prescribed after visiting a medical professional such as a General Practitioner (GP), nurse or dermatologist. There are a number of topical treatments (applied to the skin) available, such as leave-on emollients (medical moisturisers), steroid creams, coal-tar and dithranol. There is also phototherapy (light therapy) and those who have severe psoriasis may take systemic medicine tablets, such as cyclosporine and methotrexate, or have biological injections.


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