Psoriasis is a scaly skin condition which can take many forms.
It affects about one in 50 of the population, sometimes quite severely. Perhaps about one in 10 of people with psoriais will get the arthritis, and at the moment it is difficult to predict who will get the joint problems. It can affect all ages and both sexes are equally affected. The presence of psoriasis is important, but a tentative diagnosis can sometimes be made even when there is no skin rash. Blood tests are of secondary importance, and serve to confirm that there is inflammation in the joints.