I note that some viewers have been requesting some clarification of the meaning of the terms "mixed connective tissue disease" (MCTD) and "undifferentiated connective tissue disease" (UCTD).

Connective tissue diseases are a special group of rheumatic diseases (diseases that feature abnormalities of the muscles and/or joints) that can be associated with arthritis. The cause(s) for the connective tissue diseases is (are) unknown. They are characterized as a group by the presence of spontaneous over-activity of the body's immune (defense) 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 tissues diseases, but they are commonly found in the blood as an characteristic feature.

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. 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, rheumatoid arthritis, scleroderma, polymyositis, and dermatomyositis. Each of these diseases affects people in a characteristic way and causes typical findings that doctors can recognize during an examination. Each also has characteristic blood test abnormalities and abnormal antibody patterns. For example, systemic lupus erythematosus has dsDNA antibodies, while scleroderma has Sc170 antibodies. Additionally, each of these diseases can evolve either slowly or rapidly from very subtle abnormalities before demonstrating the classic features that help in the diagnosis.

When these conditions have not developed the classic features of a particular disease, doctors will often refer to the condition as "undifferentiated connective tissue disease," or UCTD. This designation implies that the characteristic features that are used to define the classic connective tissue diseases are not present, but that some symptoms or signs of a connective tissue disease exist. For example, a person may have a special antibody in the blood, such as antinuclear antibody and muscle pains, but no other definable 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.

Viewer Question: I have UCTD and I would like to know if UCTD could turn into Lupus or another connective tissue disease.

Doctor's Answer: Yes. Undifferentiated connective tissue disease (UCTD) is a condition which melts together features of various classical diseases. The classical connective tissue diseases include rheumatoid arthritis, systemic lupus erythematosus, scleroderma, polymyositis, dermatomyositis, and Sjogren's syndrome.

UCTD is referred to as "undifferentiated" because the features that it displays are not adequate as criteria for any one of the classical connective tissue diseases. These features include signs and symptoms as well as immune and blood tests of these diseases.

The fact is that UCTD can evolve slowly, even over years, to become one of the classical connective tissue diseases or it may never evolve at all. Also, the very features which suggest UCTD can resolve and the disease go away entirely.

It is anticipated that as medical science evolves, so too will the ability to better categorize and pigeon-hole various forms of UCTD into unique disease entities.