Causes of Psoriatic Arthritis
Experts aren't sure what causes psoriatic arthritis, although they do know that having skin psoriasis is the biggest risk factor. As many as 30% of people with psoriasis go on to develop psoriatic arthritis. You may also be more likely to get psoriatic arthritis if you have skin psoriasis that affects your nails. About 80% of people with psoriatic arthritis have some kind of nail psoriasis.

Genetics is another risk factor. About 40% of people with psoriatic arthritis have a family member with psoriasis or another form of arthritis. But experts believe that environment can also play a role, and some think an infection such as strep throat may kick-start the immune system, causing psoriatic arthritis to then develop.