Scientists say they have made a major breakthrough in the understanding of a mysterious skin disease.
Scleroderma thickens the skin
They hope their work, published in Proceedings of the National Academy of Sciences, will lead to better ways to diagnose and treat the condition.
Scleroderma causes painful thickening of the skin, swelling and other tissue damage.
A team from Princeton University has pinpointed 2,700 genes which may play a role in the development of the disease.
The genes appear to show unusual levels of activity in people who have the condition.
The researchers thought that the cause of the disease would be revealed by examining areas of affected skin for signs of unusual genetic activity, just as cancer researchers look for differences between tumour cells and normal ones.
However, they found that the unusual activity was not confined to affected areas of skin - seemingly healthy patches showed the same levels of activity too.
This suggests that scleroderma is present throughout the body, rather than only in areas where symptoms are visible, and that the root cause is much deeper than previously suspected.
The condition, which typically develops in people in their 40s and 50s, often produces only relatively mild symptoms. It is estimated to affect up to 8,000 people in the UK.
However, in a more severe form it can be fatal within 10 years. Thickening of the tissue in the lungs can lead to severe breathing problems, and the heart can struggle to cope as it becomes more difficult to force blood through its tissues.
No current treatments are consistently effective, and the disease is so poorly understood, that it typically takes patients more than a year to obtain a correct diagnosis.
Researcher Dr David Botstein said: "This is a disease about which very little is known.
"We have now found that whatever causes the disease is there before the symptoms appear."
The study showed that skin biopsies from four people with a severe form of scleroderma have consistently and significantly different patterns of gene activity from that of biopsies from people without the disease.
A comparison of 12,000 genes in people with and without the disease yielded 2,776 with substantially different levels of activity.
Professor Kari Connolly, of the University of California-San Francisco, said the research gave scientists "a handle on the disease".
"Somewhere in that package of 2,776 genes are the clues we need to look in a more sophisticated way at the many abnormalities that show up in this disease."
The research has already shown that the disease seems to be linked to abnormalities in antibody-producing cells, which are part of the immune system.
However, the researchers have found no evidence to back up their theory that the condition was linked to abnormalities in the gene activity of skin cells called fibroblasts.
Anne Mawdsley, director of the UK Raynaud's & Scleroderma Association, said: "New treatments are desperately needed to treat all aspects of scleroderma but especially skin, lung, heart and gut involvement.
"Eventually a cure may be possible if we understand the scientific basis of scleroderma."