We can see how connective tissues (in this case collagen) are the structural portions that essentially hold the cells of the body together. A connective tissue disease is any disease that has the connective tissues of the body as a primary target of pathology. These tissues form a framework, or matrix, for the body.
The connective tissues are composed of two major structural protein molecules, collagen and elastin. There are many different types of collagen protein that vary in amount in each of the body's tissues.
Many connective tissue diseases feature abnormal immune system activity with inflammation in tissues as a result of an immune system that is directed against one's own body tissues.