Mixed Connective Tissue and Undifferentiated Connective Tissue Disease:

Connective tissue diseases are a special group of rheumatic diseases (diseases that feature abnormalities of the muscle and/or joints) that can be associated with arthritis. The causes for the connective tissue diseases are currently unknown. They are characterized as a group by the presence of spontaneous over-activity of the body's immune system. This over-activity results in the production of unusual antibodies that are found in the blood. The antibodies themselves may or may not cause any problems in patients with connective tissue disease but they are commonly found in the blood as an characteristic feature.

The connective 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 molecules,collagen and elastin. There are many different types of collagen protein that vary in amount in each of the body's tissue. Elastin has the capability of stretching and returning to it's original length--like a rubber band or spring. Elastin is the major component of ligaments (tissues that attach bone to bone) and skin.

In patient's with connective tissue disease,it is common for collagen and elastin to become damaged by inflammation. Diseases in which inflammation of collagen tends to occur are also referred to as collagen diseases. The classic connective tissue diseases include systemic lupus erythematosus, RA, sclerodoma,polymyositis and each of these disease affects people in a charachteristic way and causes typical findings that physicians can recognize during an examination. Each disease also has characteristic blood test abnormalities and abnormal antibody patterns e.g., S.L.E. has dsDNA antibodies,while scleroderma has SC170 antibodies. Additionally,each of these can evoke either slowly or rapidly from very subtle abnormalitis before demonstrating the classic feature that help in the diagnosis.

When these conditions have not developed the classic feature of a particular disease physicians will refer to the condition as Undifferentiated connective tissue disease or UCTD. this designation implies that th characteristic features that used to define the classic connective tissue diseases are not present,but that some symptoms or signs of a connective tissue disease exists. e.g., a person may have a special antibody in the blood,such as anti nuclear antibody and muscle pains,but no other defineable features of a classic connective tissue disease. Individuals with undifferentiated connective tissue disease may never develop a fully definable condition or they may eventually develop a classic connective tissue disease.

Mixed connective tissue disease,which was first described in 1972 is "classically" considered as an "overlap" or mix of three specific connective tissue disease,SLE,sclerpderma,and polymyositis. Patients with this pattern of disease (MCTD) have features of each of the 3 diseases. They also typically have very high quantities of ANAs antinuclear antibodies and antibodies toribonucleo protein (anti-RNP) detectable in their blood. The symptoms of many of thes patients eventually evolve to become dominated by features of one of the 3 component illness ,most commonly the scleroderma features.

It is now known,however,that overlap syndrome can involve any combination of the connective tissue diseases. Therfore,e.g.,patients can have a combination of RA and SLE (hence the coined phrase "rhupus")

Accordinly,today,true mixed connective tissue disease is diagnosed when patients demonstrate the clinical features (exam findings) of overlap illness. These patients also display high amounts of ANA and anti-RNP without having such other antibodies as the dsDNA antibody of SLE and SC170 antibodies of scleroderma-systemic lupus erythematosus.

Treatment of an syndrome is geared towards treating the manifestations of its component conditions. It is conceivable (in fact,not uncommon) that a patient could be diagnosed early as having e.g., SLE,then later as the condition evolves over time,develop MCTD. Further,patients with typical MCTD early on,can evolve into classic features of a single connective tissue disease in time (most commonly scleroderma). These are chronic unpredictable illnesses. They can affect many different organs or areas of the body. Sometimes the organs can become seriously damaged and death can result. Most patients with these illnesses,however,may require little or no treatment and live a relatively normal life,depending upon on the illness or individual condition. Some patients will have serious complications.

There are many types of antinuclear antibodies (ANAs). One class of ANAs react with cell components that are extractable from the nucleus in a certain solution in the laboratory (extractable nuclear antigens). The ANA antibodies that bind to these ENAs are called anti-ENAs. Examples of anti-ENAs include SSA and SSB antibodies so called RNP and Sm antibodies

ENA antibodies are subsets of ANAs. Sjorgren's syndrome is commonly associated with SSA and/or SSB antibodies. These antibodies can also be present in other rheumatic diseases.

Some patients with MCTD can have difficulty becoming pregnant (decreased fertility). There is also some increased risk of miscarriage in women with MCTD. As to birth defects or other direct effects on the baby  of mothers with MCTD is unknown.