Psoriatic arthritis can progress without appropriate treatment by affecting more joints on both sides of the body, most commonly affecting the hands, feet, and low back. Psoriatic arthritis can also progress by worsening systemic systems (systems throughout the body), such as chronic fatigue; nail changes; tendon and ligament pain; inflammation of the eyes called uveitis; digestive symptoms such as abdominal pain, bloating, constipation, and diarrhea; and organ damage from inflammation to the heart, lungs, or kidneys.