What is juvenile idiopathic arthritis?
Juvenile
idiopathic arthritis (JIA) is the most common type of arthritis
that affects children. It used to be known as juvenile rheumatoid
arthritis, but the name was recently changed to reflect the
differences between childhood arthritis and adult forms of
rheumatoid arthritis.
JIA is a chronic (long-lasting) disease that can affect joints
in any part of the body. In this disease, the immune system
mistakenly targets the synovium, the tissue that lines the inside
of the joint. The synovium responds by making excess fluid
(synovial fluid), which leads to swelling, pain and stiffness. The
synovium and inflammation process can spread to the surrounding
tissues, eventually damaging cartilage and bone. Other areas of the
body, especially the eyes, also may be affected by the
inflammation. Without treatment, JIA can interfere with a
child's normal growth and development.
There are several main subtypes of JIA, which are based on
symptoms and the number of joints involved.
- Systemic arthritis -- Also called Still's
disease, this type occurs in about 10 to 20 percent of children
with JIA. A systemic illness is one that can affect the entire
person or many body systems. Systemic JIA usually causes a high
fever and a rash, which most often appears on the trunk, arms and
legs. It also can affect internal organs, such as the heart, liver,
spleen and lymph nodes. This type of JIA affects boys and girls
equally and rarely affects the eyes.
- Oligoarthritis -- This type of JIA affects fewer
than 5 joints in the first 6 months of disease, most often the
knee, ankle and wrist joints. It also can cause inflammation of the
eye (often the iris, the colored area of the eye), called uveitis,
iridocyclitis or iritis. About half of all children with JIA have
this type, and it is more common in girls than in boys. Many
children will outgrow this type of arthritis by adulthood. In some
children it may spread to eventually involve more joints.
- Polyarthritis -- This type of JIA affects 5 or more
joints in the first 6 months, often the same joints on each side of
the body. Polyarthritis can also affect the neck and jaw joints as
well as small joints, such as those in the hands and feet. It is
more common in girls than in boys.
- Psoriatic arthritis -- This type of arthritis
affects children who have arthritis with the rash of psoriasis.
Children frequently have nail changes that look like pitting. The
arthritis can precede the rash by many years or vice versa.
- Enthesitis-related arthritis -- This type of
arthritis often affects the spine, hips and enthesis (attachment
point of tendons to bones) and occurs mainly in boys older than 8
years. The eyes are often affected in this type of arthritis. There
is often a family history of arthritis of the back (spondylitis) in
male relatives.