While most rheumatoid arthritis cases generally affect adults, it doesn’t mean young children and adolescents aren’t immune from this disease. Juvenile idiopathic arthritis (JIA), more commonly known today as juvenile rheumatoid arthritis, is a category that focuses on other several forms of chronic arthritis in children.1
In the late 1990s, JIA was known as juvenile rheumatoid arthritis in the U.S. and juvenile chronic arthritis in Europe, but the names were changed to distinguish it further from rheumatoid arthritis in adults. It’s considered to be the most frequent chronic rheumatologic disease among children.
Various Types of Juvenile Idiopathic Arthritis
There are seven mutually exclusive categories of juvenile idiopathic arthritis, namely:2
- Polyarthritis rheumatoid factor positive
- Polyarthritis rheumatoid factor negative
- Oligoarthritis (persistent and extended)
- Psoriatic arthritis
- Enthesitis-related arthritis
- Undifferentiated arthritis
The most common cases of JIA fall under oligoarthritis (persistent and extended) and polyarthritis rheumatoid factor negative.
Just like other types of arthritis, juvenile idiopathic arthritis occurs when the body’s immune system attacks healthy cells and tissues. This leads to inflammation characterized by redness, heat, pain, and swollen joints.3 There are also other symptoms of JIA, which include:
- Limited range of motion and limping
- Tenderness when joints are moved
- Increased warmth in the joint region
- High fever and skin rashes, both of which may appear then disappear quickly
- Eye inflammation (this is a severe complication for children with oligoarthritis that can also be seen in other types of arthritis)
- Eye diseases like iritis or uveitis, which can be present at the onset of arthritis but progresses sometime after a patient first develops juvenile arthritis
- Growth problems that can result in misshapen bones or unequal bone length (it depends on the severity of the disease and the joints)
- Slowing down of overall growth
How Is Juvenile Idiopathic Arthritis Different from RA?
The major difference between rheumatoid arthritis and juvenile idiopathic arthritis lies in the age it can affect patients. RA usually attacks adults, especially the elderly, but JIA is diagnosed if the symptoms occur (even intermittently) in a child less than 16 years of age for at least six weeks.
There’s no definite cause identified for juvenile idiopathic arthritis, as doctors haven’t found out the main triggers of autoimmune diseases like JIA.
However, as the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) points out, not all cases of JIA are autoimmune. Some patients might have an auto-inflammatory condition instead.
A key difference between an autoimmune and an auto-inflammatory condition is in the way they affect the body. Autoimmune diseases involve proteins called autoantibodies, which attach to healthy tissues by mistake, sending signals for the tissues to be attacked.
Autoantibodies are different from antibodies, which are proteins produced by the body to work against bacteria and viruses and destroy them.
Meanwhile, auto-inflammatory conditions are not caused by autoantibodies, but instead involve “a more primitive part of the immune system that in healthy people causes white blood cells to destroy harmful substances.” The breakdown of the immune system then leads to inflammation, or even fever and rashes.