Juvenile rheumatoid arthritis (JRA) in children
Juvenile rheumatoid
arthritis (JRA), often referred to by doctors today as juvenile idiopathic
arthritis (JIA), is a type of arthritis that causes joint inflammation and
stiffness for more than six weeks in a child 16 years of age or younger. The
inflammation causes redness, swelling, fever, and pain in the joints, although
many children with JRA do not complain of joint pain. Any joint can be
affected, and inflammation can limit the movement of the affected joints.
JRA is an autoimmune
disease in which the body misidentifies some of its own cells and tissues as
foreign. The immune system, which normally helps fight off harmful foreign
substances such as bacteria or viruses, begins attacking healthy cells and
tissues. The result is inflammation marked by redness, fever, pain, and
swelling.
Researchers still
don't know exactly why the immune system falters in children who develop JRA,
though they suspect it's a two-step process. First, something in a child's
genetic make-up makes them prone to developing JRA. Then an environmental
factor, such as a virus, triggers the development of JRA.
JRA can cause fever
and anemia, and can also affect the heart, lungs, eyes, and nervous system.
Arthritis episodes can last several weeks and may recur, although symptoms tend
to be less severe with subsequent recurrences. Treatment is similar to that of
adults, with an additional focus on physical therapy and exercise to keep the
growing body active. However, many of the strong drugs used for adults are
usually not needed for JRA. Permanent damage from JRA is now rare, and most
affected children make a full recovery from the disease without suffering any
permanent disability.
Doctors classify JRA into
three types based on the number of joints affected, symptoms, and the presence
of certain antibodies (specific proteins produced by the immune system) in the
blood. These classifications help describe the progression of the disease.
Types of JRA
Pauciarticular
Pauciarticular means
that four or fewer joints are involved. This is the most common form of JRA;
about half of all children with JRA have this type. It usually affects large
joints, such as the knees. Girls under the age of 8 are most likely to develop
this type of JRA. Some children with small joint JRA have abnormal proteins
called antinuclear antibodies in their blood.
Eye disease affects
20-30% of children with small joint JRA and is more common in children with
abnormal antinuclear antibodies. Regular check-ups with an ophthalmologist (a
doctor who specializes in eye diseases) are necessary to treat serious eye
conditions such as iritis (inflammation of the iris or the colored part of the
eye) or uveitis (inflammation of the inner eye or choroid). Many children with
pauciarticular disease develop arthritis into adulthood, although vision
problems may persist, and in some people joint symptoms may recur.
Polyarticular
About 30% of all
children with JRA have a polyarticular lesion that affects five or more joints.
Small joints, such as those in the arms and legs, are most commonly affected,
but large joints can also be affected. Polyarticular JRA is more often
symmetrical - the same joints on both sides of the body are affected. Some
children with polyarticular disease have a special type of antibody called
rheumatoid factor in their blood. These children often have a more severe form
of the disease that doctors think is similar to rheumatoid arthritis in adults.
Systemic
In addition to joint
swelling, the systemic form of JRA is characterized by fever and a pale pink
rash, and can also affect internal organs such as the heart, liver, spleen, and
lymph nodes. The systemic form, sometimes called Still's disease, affects 20%
of children with JRA. Almost all children with this type of JRA lack both
rheumatoid factor and antinuclear antibodies. A small percentage of these
children develop arthritis in many joints and may have severe arthritis that
persists into adulthood.
The main difference
between juvenile and adult arthritis is that some children with JRA outgrow the
disease, while adults usually have symptoms for life. Research estimates that
symptoms of JRA disappear in more than half of all affected children in
adulthood. Also, unlike adult rheumatoid arthritis, JRA can affect bone
development as well as growth in children.
Another difference between JRA and adult rheumatoid arthritis is the percentage of people who test positive for rheumatoid factor in their blood. About 70-80% of all adults with rheumatoid arthritis have rheumatoid factor, but less than half of all children with rheumatoid arthritis test positive for rheumatoid factor. The presence of rheumatoid factor indicates an increased likelihood that JRA will persist into adulthood.