A
connective tissue disease is any disease that has the
connective tissues of the body as a target of pathology. Connective tissue is any type of
biological tissue with an extensive
extracellular matrix that supports, binds together, and protects
organs. These tissues form a framework, or matrix, for the body, and are composed of two major structural protein molecules:
collagen and
elastin. There are many different types of collagen protein in each of the body's tissues. Elastin has the capability of stretching and returning to its original length—like a spring or rubber band. Elastin is the major component of ligaments (tissues that attach bone to bone) and skin. In patients with connective tissue disease, it is common for collagen and elastin to become injured by inflammation. 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 (autoimmunity).