What it is
Psoriasis is an inflammatory skin disease that produces red, thickened areas covered with silvery-white scales, most often on the scalp, elbows, knees and lower back. It affects nearly one per cent of the population. Small red spots gradually enlarge and collect powdery silvery scales, and if the flakes are removed the tender skin underneath bleeds. Palms and soles may be involved on their own. Patches usually appear on both sides of the body, and the face is often spared.
Nails with psoriasis have tiny pits on them, and may loosen, thicken or crumble. About seven per cent of patients also have arthritis, which in most people is not too severe. Guttate psoriasis affects children and young adults, often after a sore throat, with multiple drop-like spots; it usually clears in a few weeks or months.
What causes it
The exact cause is not known. In psoriasis the skin sheds itself too rapidly, every three to four days. It can be hereditary in up to one in ten patients. New spots often appear 10 to 14 days after the skin is cut, scratched, rubbed or badly sunburned. Streptococcal sore throat and some medicines can set it off, and flare-ups often come in winter with remissions in summer. Psoriasis cannot be passed from one person to another, and diet generally plays no part.
How we treat it
Dermatologists diagnose psoriasis by examining the skin, nails and scalp, and may take a skin biopsy. The aim of treatment is to reduce inflammation and slow the rapid cell division. Treatment depends on your health, age, lifestyle and how severe the psoriasis is, and several visits may be needed.
Your doctor may prescribe moisturising creams and lotions, corticosteroids, tar, salicylic acid, anthralin or calcipotriol to apply. Severe psoriasis may need oral medicines — methotrexate, retinoids or cyclosporine — under very careful supervision, or PUVA, which is psoralen with ultraviolet light therapy. Localised plaques can also be treated with targeted phototherapy. Used alone or in combination, these treatments can clear or greatly improve psoriasis in most people, but psoriasis is a long-term condition and it can come back.
This page is being updated. The clinic is reviewing this information against current practice. Please ask the doctor at your consultation.