Scleroderma is a group of rare autoimmune diseases that involve the hardening and tightening of the skin and connective tissues. It can also cause problems in the blood vessels, internal organs, and digestive tract. Scleroderma is often categorized as "limited" or "diffuse," which refers only to the degree of skin involvement. Localized scleroderma affects only the skin, while systemic scleroderma may affect large areas of skin and organs such as the heart, lungs, or kidneys. The cause of scleroderma is unknown, but researchers think that the immune system overreacts and causes inflammation and injury to the cells that line blood vessels. This triggers connective tissue cells, especially a cell type called fibroblasts, to make too much collagen and other proteins, leading to some of the signs and symptoms of scleroderma. Symptoms of scleroderma may include thickening and swelling of the fingers, joint pain, taut, shiny, darker skin on large areas, limited mobility or immobile fingers, wrists or elbows because of the thickening of the skin, calcium bumps on fingers or other bony areas, and sores on fingertips and knuckles. While there is no cure for scleroderma, treatments can ease symptoms, slow progression, and improve quality of life.