Undifferentiated connective tissue disease (UCTD) is a condition in which a patient's symptoms don't quite meet the "criteria" (the markers or indicators doctors use to make a diagnosis) of a well-defined connective tissue disease, such as rheumatoid arthritis (RA), lupus or scleroderma. A person with UCTD may have one or more of the symptoms found in these types of connective tissue diseases, but not enough of them to make the diagnosis for any one of them. The lab tests for these diseases may even be negative (suggesting the disease is not present) in patients with UCTD.
The below is a brief overview of UCTD. For a more detailed discussion, read Undifferentiated Connective Tissue Disease – In-Depth Overview.
Occasionally, pleuritis (inflammation of tissues in the lungs and chest cavity) or pericarditis (inflammation of the lining surrounding the lungs or heart, respectively, which can cause chest pain especially with breathing) or neuropathy (abnormal nerve sensations, usually in the fingers or toes, ranging from numbness to tingling to pain) may occur. Problems with the kidneys, liver, lungs or brain are extremely rare. The problems seen with UCTD usually are not life-threatening and, typically, they do not worsen over time.
The exact cause is not well understood, however, UCTD is believed to be triggered by environmental factors (such as exposure to certain bacteria or viruses) and/or genetics (biological characteristics inherited from a person's parents). Like other, well-defined connective tissue diseases, UCTD is thought to be a systemic autoimmune disorder. For unknown reasons, the immune system, which normally fights off invaders such as bacterial and viral infections, may start to think of the body itself as foreign and begin to fight against it. Luckily, in UCTD, the autoimmunity seems to occur at low levels, because there is not much tissue damage seen in patients with UCTD. UCTD is not contagious.
Studies to date have shown that the likelihood of developing a defined connective tissue disease such as lupus is very small. Less than one-third of patients ultimately turn out to have a well-defined connective tissue disease. The longer a patient stays diagnosed as "undifferentiated," the greater the likelihood that another disease will never develop. Just as many, if not more patients with UCTD go into remission, with their symptoms disappearing.