The RNP antibody is a protein that targets ribonucleoproteins in the body’s connective tissue.
An RNP antibody test can determine if you have elevated levels of RNP antibody and possibly an autoimmune condition called mixed connective tissue disease (MCTD).
MCTD is correlated with a positive RNP antibody test and is considered an overlap disease because individuals who are diagnosed with MCTD experience symptoms characteristic of multiple autoimmune connective tissue diseases.
Currently, there is no scientific evidence supporting specific treatment options for MCTD.
When your immune system is functioning properly, your body produces protective proteins called antibodies. These proteins usually target antigens, or foreign substances. However, when you have an autoimmune disease, some of your antibodies mistakenly mistakenly attack your own cells. We call antibodies that target an individual’s own tissue autoantibodies.
One such autoantibody is the anti-U1-ribonucleoprotein (RNP) antibody, or U1-RNP antibody. As its name suggests, the RNP antibody targets ribonucleoproteins in your body. Although these proteins sound very technical, they are simply RNA–protein complexes that help your cells regulate protein production. RNA is a molecule, similar to DNA, that helps make proteins in our bodies. (Source)
In this post, we explore the role of the RNP antibody, how the RNP antibody is linked to mixed connective tissue disease (MCTD), and what an RNP antibody test can tell you about your immune health.
Researchers are not yet sure how the RNP antibody disrupts protein production. However, the RNP antibody is thought to affect the nucleus of cells, where DNA is stored. The nucleus is also where ribonucleoproteins, the proteins this antibody targets, take part in protein production. Because of this role, the RNP antibody is grouped with other antinuclear antibodies. (Source)
Although there has been limited research done on the RNP antibody, we do know there are correlations between high levels of RNP antibody and certain systemic rheumatic diseases such as mixed connective tissue disease (MCTD) and systemic lupus erythematosus (SLE). RNP antibody is also correlated with Raynaud’s phenomenon, which involves a change in color of the fingers and increased finger sensitivity to the cold. (Source, Source, Source)
It may take years to diagnose an autoimmune disease, but antibody tests can speed up this process. Testing for RNP antibody is especially helpful in diagnosing MCTD and rheumatic diseases such as:
There are different antibody tests that can be performed to check for the presence of RNP antibody including:
The results of an RNP antibody test may be considered negative, borderline, or positive. As with other tests, normal ranges may vary according to the lab, but the following general guidelines apply:
We talk about mixed connective tissue disease, or MCTD, but what does this term mean?
Autoimmune connective tissue diseases, such as SLE and dermatomyositis, are diseases in which the immune system targets connective tissue in the body, such as skin or bones. While these diseases have some common characteristics, they are distinct from one another.
MCTD, however, is a type of overlap syndrome because individuals with MCTD experience symptoms that are characteristic of multiple autoimmune connective tissue diseases. The symptoms overlap and make it difficult to determine which autoimmune disease an individual may have.
There is also a great deal of debate on whether MCTD should be considered a distinct autoimmune disease. Patients who initially appear to have MCTD may eventually be diagnosed with one specific autoimmune connective tissue disease. Should health care providers diagnose a patient with MCTD, or wait until the patient has symptoms of one established connective tissue disease?
Another issue is that the definition of MCTD is muddled and health care professionals are not yet sure of the prognosis for patients with MCTD. Overall, MCTD looks to be a placeholder name until connective tissue diseases are better understood. (Source, Source)
An estimated 95% to 100% of people diagnosed with MCTD have very high levels of RNP antibody. If your RNP antibody level is high, you may very well receive a diagnosis of MCTD, although you may later be determined to have a specific connective tissue disease. Overall, a diagnosis of MCTD is made on the basis of your symptoms as well as clinical features such as laboratory testing results. However, there is no clear diagnostic criteria. (Source, Source)
MCTD is considered by some to be a distinct autoimmune disease with symptoms characteristic of the autoimmune connective tissue diseases SLE, systemic sclerosis, and polymyositis. Symptoms vary but commonly include:
Currently, there is no scientific evidence supporting a treatment option specifically for MCTD, because MCTD itself is not yet accepted as an autoimmune connective tissue disease.
Until we know more about MCTD, you’ll need to work with your health care provider on a treatment plan that addresses the symptoms you’re having.
For example, if you are experiencing symptoms of SLE, consider using sun protection, modifying your diet or exercise routine as needed, or asking your health care provider about corticosteroids, immunosuppressants, or other medication options. (Source, Source)
The RNP antibody is an autoantibody that targets ribonucleoproteins in the body. A high level of the RNP antibody is strongly correlated with an autoimmune connective tissue disease called MCTD. However, because MCTD is not yet accepted as a distinct autoimmune disease, no specific treatment plan is available. Further research must be conducted to understand MCTD.