Connective tissue disease

Overview
A connective tissue disease is any disease that has the connective tissues of the body as a primary 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).

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, and can also be caused by environmental factors.

Heritable Connective Tissue Disorders

 * Marfan syndrome - a genetic disease causing abnormal fibrillin.
 * Ehlers-Danlos syndrome - causes progressive deterioration of collagens, with different EDS types affecting different sites in the body, such as joints, heart valves, organ walls, arterial walls
 * Osteogenesis imperfecta (brittle bone disease) - caused by insufficient production of good quality collagen to produce healthy, strong bones.

Weakly or Non-Heritable Connective Tissue Disorders
These are the autoimmune CTDs, where the cause is unknown but may have both genetic and environmental links. Weaker genetic factors may create a predisposition towards developing these autoimmune diseases. 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 classic collagen vascular have a "classic" presentation with typical findings that doctors can recognize during an examination. Each also has "classic" blood test abnormalities and abnormal antibody patterns. However, each of these diseases can evolve slowly or rapidly from very subtle abnormalities before demonstrating the classic features which help in the diagnosis. The classic collagen vascular diseases include:
 * Scurvy - caused by a dietary deficiency in vitamin C, leading to abnormal collagen.
 * Systemic Lupus Erythematosus (SLE) - An inflammation of the connective tissues, SLE can afflict every organ system. It is up to nine times more common in women than men and strikes black women three times as often as white women. The condition is aggravated by sunlight.
 * Rheumatoid Arthritis - Rheumatoid arthritis is a systemic disorder in which immune cells attack and inflame the membrane around joints. It also can affect the heart, lungs, and eyes. Of the estimated 2.1 million Americans with rheumatoid arthritis, approximately 1.5 million (71 percent) are women.
 * Scleroderma - an activation of immune cells which produces scar tissue in the skin, internal organs, and small blood vessels. It affects women three times more often than men overall, but increases to a rate 15 times greater for women during childbearing years, and appears to be more common among black women.
 * Sjögren's syndrome - also called Sjögren's disease, is a chronic, slowly progressing inability to secrete saliva and tears. It can occur alone or with rheumatoid arthritis, scleroderma, or systemic lupus erythematosus. Nine out of 10 cases occur in women, most often at or around mid-life.
 * Myositis - Myositis involves inflammation that results in damage to muscle fibers and skin. Myositis is a term that describes several illnesses including polymyositis, dermatomyositis and inclusion body myositis. Polymyositis involves inflammation of the muscles and can affect many parts of the body. Dermatomyositis involves inflammation of skin. Inclusion myositis is similar to polymositis, but its onset is generally slower and more relentlessly progressive.  All of these fall into the category of inflammatory muscle diseases - "myo" means "muscles" in Greek; "itis" means "inflamed". "Derma", which means "skin", implies the skin-related signs and symptoms that accompany the muscle inflammation of dermatomyositis.
 * Mixed Connective Tissue Disease - Mixed connective-tissue disease (MCTD) is a disorder in which features of various connective-tissue diseases (CTDs) such as systemic lupus erythematosus (SLE); systemic sclerosis (SSc); dermatomyositis (DM); polymyositis (PM); and, occasionally, Sjögren syndrome can coexist and overlap. The course of the disease is chronic and usually milder than other CTDs. In most cases, MCTD is considered an intermediate stage of a disease that eventually becomes either SLE or Scleroderma.