What is a connective tissue disease?
A connective tissue disease is any disease that has the connective tissues of the body as a primary target of pathology. The connective tissues are the structural portions of our body that essentially hold the cells of the body together. 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. 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 diseases, 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).
Diseases in which inflammation or weakness of collagen tends to occur are also referred to as collagen diseases. Collagen vascular disease is a somewhat antiquated term used to describe diseases of the connective tissues that typically include diseases which can be (but are not necessarily) associated with blood-vessel abnormalities.
Connective tissue diseases can have strong or weak inheritance risks
Connective tissue diseases that are strictly due to genetic inheritance include Marfan syndrome (can have tissue abnormalities in the heart, aorta, lungs, eyes, and skeleton) and Ehlers-Danlos syndrome (many types may have loose, fragile skin or loose [hyperextensible] joints depending on type).
Other diseases of connective tissue cannot be regularly defined by gene abnormalities. These connective tissue diseases occur for unknown reasons but may have weaker genetic factors that predispose to their development. They are characterized as a group by the presence of spontaneous overactivity of the immune system which results in the production of extra antibodies into the circulation. The connective tissue diseases include systemic lupus erythematosus, rheumatoid arthritis, scleroderma, polymyositis, and dermatomyositis. These are considered classic collagen vascular diseases. Each of these diseases has a “classic” presentation with typical findings that doctors can recognize during an examination. Each also has various typical blood test abnormalities and a variety of abnormal antibodies that are commonly found in blood testing. However, each of these diseases can evolve slowly or rapidly from very subtle abnormalities before demonstrating the classic features which help in the diagnosis.
Sometimes, in the early stages, doctors simply refer to the “undifferentiated” condition as a collagen vascular disease or undifferentiated connective tissue disease until more defined symptoms appear. The change into a more definable disease may occur over years or never happen. Furthermore, the undifferentiated features may, themselves, disappear at which point there is no disease at all.