Understanding the Link Between ACPA and Rheumatoid Arthritis: Essential Information
In a nutshell, the immune system goes rogue in people with rheumatoid arthritis (RA), attacking their own tissues, causing discomfort and inflammation in the joints. One of the antagonists in this unwanted war is anti-citrullinated protein antibodies (ACPAs), which single out proteins that have undergone citrullination – a process where an enzyme called peptidyl-arginine deiminase (PAD) switches a protein building block called arginine into citrulline.
Let's decipher how ACPAs factor into RA, why they materialize, and their role in diagnosis. A positive ACPA test can be a clue that points towards RA, but it isn't a definite diagnosis. A rheumatoid factor (RF) test could also be positive, indicating RA. Doctors use ACPA and RF levels in combination when determining the RA diagnosis, as both indicators can reveal different aspects of disease development.
For example, if you test positive for ACPA and RF, it's likely you have RA and may experience more severe symptoms. Conversely, having a positive ACPA test but no RF indicates early RA or a potential risk of RA in the future. However, a negative ACPA and RF test doesn't rule out RA. If the tests are positive for ACPAs and RA, you might be dealing with different autoimmune conditions, such as systemic lupus erythematosus (SLE) or Sjogren's disease, but this is relatively uncommon.
ACPA-positive and ACPA-negative RA present differently – the former characterizes continuous low-level joint inflammation during periods of remission, while the latter responds better to treatment with disease-modifying antirheumatic drugs (DMARDs) in the first year of therapy [1]. ACPA-positive RA also causes more damage to bones, especially the fifth metatarsophalangeal joint (little toe joint) [2]. Moreover, environmental factors like smoking might impact RA development more significantly in ACPA-positive patients [3].
So, how does the immune system produce ACPAs? The immune system responds to an overactive PAD process, in which the enzyme converts excessive amounts of arginine into citrulline. Potential culprits for this overactivity include smoking or air pollution. ACPAs subsequently attack the newly formed citrullinated proteins, setting off an inflammation loop that leads to tissue damage.
Medical professionals can spot ACPAs through a simple blood test for CCP antibodies, a type of ACPA. However, other conditions, like SLE, Sjogren's disease, tuberculosis, or chronic lung disease, may also cause raised CCP antibodies, requiring further examination.
In the end, ACPAs play a significant role in RA diagnosis and treatment planning, and comprehending their impact is crucial in tackling this autoimmune condition.
- The immune system's attack on the tissues in people with rheumatoid arthritis (RA) is aided by anti-citrullinated protein antibodies (ACPAs), which single out citrullinated proteins.
- A positive ACPA test can suggest the potential presence of RA, but it is not a definitive diagnosis.
- Doctors use a combination of ACPA and rheumatoid factor (RF) levels to determine an RA diagnosis, as both indicators can reveal different aspects of disease development.
- If a person tests positive for both ACPA and RF, they may have RA and potentially more severe symptoms.
- A positive ACPA test but no RF could indicate early RA or a potential risk of RA in the future.
- ACPA-positive RA can cause more damage to bones, particularly the fifth metatarsophalangeal joint (little toe joint), and smokers may be more susceptible to RA in ACPA-positive cases.
- Medical professionals diagnose ACPAs through a simple blood test for CCP antibodies, a type of ACPA, but other medical conditions like SLE, Sjogren's disease, tuberculosis, or chronic lung disease may also cause raised CCP antibodies.
