What Is It?

Scleroderma is a poorly understood illness that causes widespread hardening of the skin, especially on the hands and face. It also can damage the lungs, heart, kidneys, digestive tract, muscles and joints. It is a long-lasting (chronic) autoimmune disorder, an illness in which the body's immune defenses mistakenly attack the body's own cells rather than protecting them from outside invaders. Scleroderma also is called progressive systemic sclerosis.

There are two types of scleroderma. In the limited form, also called limited systemic sclerosis, the skin is the primary target. In the diffuse form (diffuse systemic sclerosis), the damage not only affects the skin, but also can affect the lungs, kidneys and other internal organs.

In people with scleroderma, scientists have identified abnormal immune proteins called autoantibodies, which are programmed to attack specific components of body cells. They also have found abnormal accumulations of protective T cells (white blood cells that are part of the immune system) in the skin and elsewhere. Although scientists don't understand exactly what happens, they believe that the immune system, perhaps involving these autoantibodies or T cells, somehow damages the body's smallest arteries, called arterioles. These damaged arterioles leak fluid, which causes swelling. They also release chemical factors that stimulate cells called fibroblasts to produce too much collagen, a fibrous protein. In the skin, this leads to thickening, hardening and tightness. Elsewhere in the body, the autoimmune attack of scleroderma can damage the digestive tract, the linings of joints, the outside sheaths of tendons, muscles (including the heart muscle), portions of the heart that regulate heart rhythm, the small blood vessels and the kidney.

Scleroderma affects about 14 in every 1 million people worldwide, and it is most common in women aged 35 to 54. Because scleroderma is more common in women during the childbearing years, researchers have looked for a pregnancy-related factor to explain why scleroderma develops. One theory suggests that leftover fetal cells can still be circulating in the mother's bloodstream decades after pregnancy, and may play some role in triggering the autoimmune changes behind scleroderma.