Overview

Sometimes symptoms of Crohn's disease can develop outside the digestive tract in other parts of the body (systemic symptoms), including the eyes, liver, blood, and bones. These systemic symptoms suggest that the immune system is involved in Crohn's disease. Systemic symptoms can include:^{footnote 1}

• Joint problems, which occur in 5% to 20% of people who have Crohn's disease. Some people develop colitis-related arthritis, which may resemble rheumatoid arthritis.
• Eye problems, which happen in up to 11% of people who have Crohn's disease. These can include ulcers on the cornea, inflammation of the iris and blood vessels (uveitis), and inflammation of the white part of the eyes (sclera).
• Skin conditions, which happen in about 10% to 20% of people who have Crohn's disease. Examples include mouth ulcers and pyoderma gangrenosum, which is an eruption of painful, spreading ulcers that usually occur on the legs. The ulcers may be blue in the centre with red edges. Mouth ulcers are more common than pyoderma gangrenosum, which is fairly rare.
• Disorders of the liver and gallbladder, which affect 10% to 35% of people who have Crohn's disease. These can include gallstones, cirrhosis of the liver, bile duct inflammation and scarring (sclerosing cholangitis) or, in rare cases, bile duct cancer.
• Low bone density. This happens in 3% to 30% of people who have Crohn's disease. The risk is greater for people who take corticosteroid medicines. It can lead to osteoporosis and, later, broken bones. More than half of people who take steroids for the long term get osteoporosis.
• Kidney stones.