The thickened skin that is associated with scleroderma is caused by your body having too much of a substance called collagen. Collagen is a normal part of skin, bones, cartilage, lungs, and just about every organ in the body. Collagen is important in helping the body repair itself after injury. In scleroderma, for some unknown reason, the dermis layer of the skin produces too much collagen. This overproduction of collagen can happen in large or small areas or may occur in a line (also called linear scleroderma).
It can start in the hands and progress to other parts of the body. It can even occur in the internal organs (also called systemic scleroderma).