There are several different patterns of psoriasis.
Plaque psoriasis is the most common and it affects the outer surfaces of the arms and legs.
Sometimes, little pockets of pus can appear anywhere on the body. This form is referred to as pustular psoriasis and can cause the patient to feel sick and feverish.
The most debilitating and painful type is erythrodermic psoriasis. The whole body will look very red and swollen, with lots of shedding of dead skin.
No one knows exactly what causes psoriasis. It can affect the young and the old.