Psoriasis rosea is a kind of autoimmune disease. It appears in different forms such as arthritis ( joints inflammation) and patches as you said.

There are some possible chances where gene therapy can cure this condition. As a prophylaxis, I would recommend you to give more emphasis in your feeding habit. You should be very cautious and try to avoid bacterial contamination in any circumstances.

If you do so. Your life longevity remains constant and physical condition will also improve. Have courage!

You can find more detail in websites

http://www.skincarephysicians.com/psoriasisnet/whatis.html