Psoriasis is a common skin disorder affecting up to 5% of some population groups.
In addition to the skin, the joints may be involved in up to 30% of sufferers, resulting in a specific type of arthritis.
Psoriasis of the skin is usually located over the elbows and knees. Any area may however be affected, including armpits, groin, palms and soles, as well as nails.
Although the scalp is another favoured site of psoriasis, the condition does not cause baldness, and only rarely does it affect the face.