Scleroderma (sklair-oh-DUR-muh), also known as systemic sclerosis, is a group of rare diseases that involve the hardening and tightening of the skin. It may also cause problems in the blood vessels, internal organs and digestive tract. Scleroderma results from an overproduction and accumulation of collagen in body tissues. Collagen is a fibrous type of protein that makes up your body's connective tissues, including your skin. Doctors don't know exactly what causes this process to begin, but the body's immune system appears to play a role.