Among patients with psoriasis, arthritis develops in up to 42% of the patients. Average of 1 case of arthritis among 4 with skin psoriasis. The prevalence of psoriatic arthritis is equal in males and females. Children of parents with psoriasis are three times more likely to have psoriasis. They are also at a greater risk of developing psoriatic arthritis. So the juvenile form of psoriatic arthritis typically presents between the ages of nine to 12 years.