What is juvenile idiopathic arthritis?
Juvenile idiopathic arthritis (JIA) is a type of inflammatory arthritis that affects children under the age of 16. It was previously known as juvenile rheumatoid arthritis (JRA).
Most forms of JIA are autoimmune. That means your body’s immune system mistakes your own cells for foreign ones and attacks them. The attacks cause joint pain, swelling, and stiffness. An infectious organism such as Streptococcal bacteria can trigger an attack.
You might have a single attack of JIA, or symptoms may last for years. The condition is considered chronic if the symptoms linger for more than three months.
Types of JIA
There are six types of JIA.
Oligoarthritis
Oligoarthritis (previously called pauciarticular JRA) affects four or fewer joints in the first six months. The joints most often affected are the knees, ankles, and elbows. Hip joints aren’t affected, but inflammation in the eye (uveitis) can occur. If antinuclear antibodies (ANA) are present, children who have them need to be monitored closely by an ophthalmologist.
Polyarthritis
Polyarthritis (also called polyarticular JIA) involves more of the body than oligoarthritis. It affects five or more joints in the first six months of illness. Small joints in the fingers and hand are most affected; it may also affect weight-bearing joints such as the knees and jaw.
There are two forms: RF-positive (rheumatoid factor-positive) and RF-negative (rheumatoid factor-negative). The RF-positive type most closely resembles adult rheumatoid arthritis.
Systemic JIA
Systemic JIA affects the entire body, sometimes including internal organs such as the heart, liver, and spleen. Symptoms can include high fevers, rashes, anemia, and lymph node enlargement.
Other subtypes
Other subtypes include psoriatic and enthesitis-related JIA:
- Psoriatic JIA occurs when psoriasis is present alongside other symptoms such as nail pitting, nail separation (onycholysis), and the swelling of a single whole finger or toe (dactylitis).
- Enthesitis-related JIA involves inflammation of the tendons, ligaments, spine (axial), and sacroiliac (SI) joints. It can also affect the hips, knees, and feet. Uveitis can occur as can the genetic marker HLA-B27.
The last subtype is undifferentiated arthritis, which does not fit within any other subtype. Symptoms can span two or more of the subtypes.
Arthritis symptoms can flare up
The symptoms of arthritis come and go in waves called flare-ups. During a flare-up, symptoms worsen. Symptoms go into remission — become less severe or disappear — between flare-ups.
JIA is different in everyone. You may have a few flare-ups and then never have symptoms again. You may also experience frequent flare-ups or flare-ups that never go away.
Joint pain and other problems
The most common symptom of JIA is joint pain. Joints may swell and grow tender. They can turn red and feel warm to the touch. Your joints can become stiff and lose their mobility. This results in a loss of fine dexterity, especially in your hands. Many people with JIA limp due to joint pain in their hips, knees, or ankles.
You might find yourself becoming less physically active due to the pain and loss of mobility. If your arthritis lasts long enough, your joints may become damaged.