Arthritis - psoriatic; Psoriasis - psoriatic arthritis; Spondylitis - psoriatic arthritis
Psoriasis is a common skin problem that causes red patches on the body. It is an ongoing (chronic) inflammatory condition. About 1 in 20 people with psoriasis may develop arthritis with the skin condition. Nail psoriasis is linked to psoriatic arthritis.
In most cases, psoriasis comes before the arthritis.
The cause of psoriatic arthritis is not known. Genes, immune system, and environmental factors may play a role. It is likely that the skin and joint diseases may have similar causes. However, they may not occur together.