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 is rare, affecting about 14 in every 1 million people worldwide. It is most common in women aged 35 to 54. The cause is unknown. For some reason, cells called fibroblasts make too much scar-type tissue in the skin and in organs throughout the body.
A number of theories have been proposed to explain this, including abnormalities in blood vessel function, abnormal proteins and antibodies in the circulation, and abnormal amounts of chemical messengers instructing fibroblasts to become overly active. 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. Genetic factors and infectious triggers have also been proposed.
Older studies have linked scleroderma to exposure to certain chemicals, including vinyl chloride, epoxy resins, aromatic hydrocarbons and ingestion of rapeseed oil adulterated with aniline. Some people who took tryptophan, an amino acid that used to be sold as a dietary supplement, developed a condition similar to scleroderma called eosinophilia myalgia syndrome. Since tryptophan was removed from the market, no further cases of eosinophilia myalgia syndrome have been reported. But the clear link between tryptophan and eosinophilia myalgia syndrome and the scleroderma-like disease associated with contaminated rapeseed oil ingestion raise the possibility that exposure to something in the environment could trigger scleroderma.