In fact, this hard skin is the most visible symptom of scleroderma. It is thought to be an autoimmune rheumatic disease. This means that the immune system begins working against the body's healthy cells.
Specifically, scleroderma is characterized by an overabundance of collagen as the immune system affects the body's connective tissue.
Collagen is the fibrous protein found in the bones and connective tissue. Obviously, problems arise when there becomes too much of it.