Psoriasis

Psoriasis is a long-term condition in which the immune system becomes overactive and drives the skin to make new cells much faster than it sheds old ones. The extra cells pile up into raised patches, called plaques, covered in scale.

It often first appears between the ages of about 15 and 25, or later between about 50 and 60. Flare-ups can last weeks or months, then the skin settles. Psoriasis cannot be cured, but treatment controls it well for most people.

The usual sign is patches of dry, thickened, flaky skin that can itch, burn or feel sore. On lighter skin they look pink or red with silvery-white scale; on brown and black skin they often look grey or darker, and may leave dark marks after healing.

• Common sites: elbows, knees, scalp, lower back, chest and skin folds
• Nails with small dents or pits, thickening, or lifting from the nail bed
• Small drop-shaped spots on the trunk and limbs, often after a throat infection

See a doctor within a few days for a new scaly rash, for patches that are spreading, cracking or bleeding, for treatment that has stopped working, or for joint pain, stiffness or swelling.

Psoriasis comes from a mix of inherited tendency and the immune system. Immune cells release signals that inflame the skin and speed up the making of new skin cells, so they reach the surface in days rather than weeks.

Flares are often set off by stress, a throat or other infection, an injury to the skin such as a cut, scratch or sunburn, cold dry weather, smoking, heavy drinking, and certain medicines. Stopping steroid tablets can also trigger a flare.

• A parent, brother or sister with psoriasis
• Smoking or chewing tobacco
• Being overweight
• Drinking a lot of alcohol
• Repeated throat infections, especially in young people
• Long-standing stress
• Some prescribed medicines

The same inflammation can reach the joints. Psoriatic arthritis causes pain, stiffness and swelling, often in the fingers, toes, knees or lower back, and can damage joints if it is not treated.

Psoriasis is also linked with heart attacks and strokes, type 2 diabetes, obesity and eye inflammation. Because it is visible, it often affects confidence, sleep and mood, and anxiety and depression are common.

Psoriasis cannot be prevented, but flares can be made fewer and milder:

• Moisturise daily to keep scale soft and reduce cracking
• Stop smoking and chewing tobacco
• Keep to a healthy weight and stay active
• Limit alcohol
• Protect the skin from cuts, scratches and sunburn
• Treat throat and other infections promptly
• Tell any doctor you have psoriasis before starting a new medicine

Psoriasis is nearly always diagnosed by examining the skin, scalp and nails and asking about symptoms, recent illness, stress, medicines and family history. The doctor also checks whether joints are tender or swollen.

A small skin sample is sometimes taken to separate psoriasis from other rashes, such as eczema or a fungal infection. Blood tests may be arranged before certain treatments.

Treatment is stepped to how much skin is involved and how much it affects daily life. For mild and moderate psoriasis it is applied to the skin: moisturisers, preparations based on vitamin D, steroid creams and ointments, coal tar, and preparations related to vitamin A. Scalp psoriasis has its own shampoos and lotions.

If that is not enough, a specialist may advise light treatment, in which measured doses of ultraviolet light are given in a clinic. Widespread or stubborn psoriasis, and psoriatic arthritis, are treated with tablets or injections that calm the immune system. These need regular blood tests and monitoring.