What is arthritis?
Arthritis means "joint inflammation" and refers to a group of illnesses that cause pain swelling, stiffness and loss of motion in the joints.
Arthritis is a general term that refers to the more than 100 disorders in the joints that cause pain, swelling and stiffness in supporting structures of the body, such as the muscles, tendons, ligaments and bones. Rheumatic or rheumatoid arthritis, as opposed to osteoarthritis, can also affect other parts of the body, including various internal organs.
While children can develop almost all types of arthritis that adults get, when they have rheumatoid arthritis, it is called juvenile rheumatoid arthritis or JRA.

What is juvenile rheumatoid arthritis?
Juvenile rheumatoid arthritis is diagnosed after joint inflammation and stiffness is present in your child for more than six weeks. It typically occurs in children, ages 6 months to 16 years.
The inflammation from JRA causes redness, swelling, warmth and soreness in the joints. Any joint can be affected, while inflammation limits the mobility of affected joints. Systemic JRA also affects  the internal organs. Doctors classify JRA into three types, according to the number of joints involved, the symptoms, and the presence or absence of certain antibodies found by blood tests. (Antibodies are special proteins made by the immune system). These classifications help the doctor determine how the disease will progress and whether the internal organs and/or skin are affected.
It is important to note that many children in the initial stages of JRA do not complain of joint pain or stiffness.

Pauciarticular JRA (paw-see-are-tick-you-lar)
Pauciarticular means that four or fewer joints are affected. Pauciarticular is the most common and least severe form of JRA; about 40 to 60 percent of all children with JRA have this type. Usually, large joints (knees, ankles or elbows) are involved. Other joints such as wrists, spine and even small finger or toe joints can be affected, but less commonly. Pauciarticular JRA often affects a particular joint on one side of the body, rather than on both sides at the same time (both sides involved is called "symmetrical arthritis").

Eye inflammation or uveitis (explained under Eye Care) affects 20 to 30 percent of children with pauciarticular JRA. Of these children, up to 80 percent test positive for an antibody called antinuclear antibody or ANA. In these children, JRA tends to develop at a particularly early age. 
Regular examinations by an ophthalmologist (a doctor who specializes in eye diseases) are necessary to prevent serious eye problems such as iritis (inflammation of the iris, the colored part of the eye) or uveitis. Some children with pauciarticular illness outgrow JRA by adulthood, while eye problems and joint symptoms may recur over the years.

There are two types of pauciarticular JRA. About one-third of pauciarticular cases, usually affecting girls under age 7, are associated with the development of chronic uveitis and with positive testing for ANA. This condition generally lasts for years. Because this eye condition is silent, proper diagnosis and monitoring by an eye doctor who is familiar with this complication is essential. Periodic checkups should continue into the teenage years.

The second type of pauciarticular JRA usually affects boys over age 8, and tends to involve the lower spine (sacroiliac joints), hips, knees, ankles and tendons. In some cases, the spots at which tendons and ligaments attach to bones are also inflamed. These children may also develop uveitis, and it is usually acute (an illness of short duration, progressing rapidly and in need of urgent care).
This type of JRA may be the first sign of another arthritis-related condition, such as one of the spondyioarthropathies. This latter group of illnesses affects the spine, tendons and eyes, and is associated with a genetic factor, a human leukocyte antigen in the blood, called HLA-B27. An HLA-B27 test may be ordered to determine if the child has this.
Some children with pauciarticular JRA develop long-term problems such as chronic damage in the eyes, even after the joint problems are in remission.
Other children develop chronic joint problems. These can include decreased range of motion of a joint, shortening or lengthening of a limb, finger or toe, damaged cartilage and/or enlargement of a joint. In some children, the arthritis spreads to other joints. These children are said to have "extended pauciarticular JRA" which is similar to polyarticular JRA.

While many children have repeated cycles of flare-ups and remissions, other children are completely free of the illness within a few years of diagnosis.

Polyarticular JRA is often symmetrical (suh-meh-trih-kul)
Polyarticular means many joints. This form of arthritis, affecting four or more joints, is severe due to the greater numbers of joints involved and the fact that it tends to progress over time. Girls are affected by polyarticular JRA more frequently than boys are. The illness is also most common in children up to age 3 or after the age of 10.
When polyarticular JRA affects teenagers, it resembles adult rheumatoid arthritis. Some children with polyarticular have an antibody in their blood called IgM rheumatoid factor (RF). About 30 to 40 percent of all children with JRA have polyarticular disease.

Polyarticular arthritis usually affects the small joints of the fingers and hands, and can affect weight-bearing joints (including the knees, hips and ankles), as well as the neck and jaw.
When polyarticular affects the same joints on both sides of the body, it is called symmetrical. For example, a child with polyarticular JRA might have problems with the joints in both the left and right hands. Other symptoms are inflammation of internal organs, and anemia (low red blood cell count).

Children with polyarticular JRA, especially girls who test positive for ANA, are at risk of developing chronic uveitis, as are those with pauciarticular disease. Ophthalmologists should evaluate these children.

Children with polyarticular JRA may experience slow growth in the jaw due to inflammation in the TMJ (temporomandibular joint), causing jaw pain and discomfort with chewing. This condition might affect personal dental care, eating habits and normal growth rates.

If there is damage to the spine, neck stiffness and difficulty turning the head side to side may occur. Your doctor may order special x-rays to help determine if arthritis has developed in these areas.

Since polyarticular JRA affects many more joints than does pauciarticular JRA, your child may need to use several different medications (often taken together) to be treated successfully.

In severe cases, steroids may be necessary for a period of time, but they are not usually a long-term solution. While taking steroids will create a temporary feeling of great well-being, long-term use can cause problems such as short stature and weak bones. When a child is put on steroids, the goal is to get him or her off the medication as soon as possible. Non-steroidal anti-inflammatory drugs are generally sufficient for many children with polyarticular JRA.

Juvenile psoriatic arthritis (siseiar-es)
A skin illness called psoriasis can accompany JRA. When arthritis and psoriasis occur together, the illness is called psoriatic arthritis, affecting both the joints and the skin.
Juvenile psoriatic arthritis commonly causes red scaly patches to appear on the skin. These scaly patches further cause bypsoriasis, also known as psoriatic plaques, or areas of inflammation and excessive skin production, occurring on the elbows and knees, as well as on the hips, back, fingers and toes. Skin rapidly accumulates at these sites and takes on a silvery-white appearance. Children with this type of JRA also often have pits or ridges in their fingernails.
This type of arthritis, occurring at any age, initially shows up in fewer than four joints, but later goes on to include multiple joints (appearing similar to polyarticular JRA). About half of the children who contract psoriatic arthritis have other arthritis symptoms before there is any sign of skin illness. For this reason, a family history of psoriasis will help your doctor diagnose psoriatic arthritis, which can progress to become a serious, disabling problem.
Systemic onset JRA (sis-teh-mik)
A systemic illness is one that affects the entire body, rather than a few specific parts. This least common form, also known as Still’s Disease, occurs in 10 to 20 percent of all children with JRA. Boys and girls are equally likely to have systemic onset JRA, which is associated with high fevers, a rash and, in some cases, inflammation of internal organs. For some children, systemic symptoms and fever may go away completely after a few months, although the joint-related symptoms may remain for a longer period.

Symptoms of systemic onset of JRA include: daily, high spiking fevers (103 degrees or higher) that may last for weeks or even months; a rash of pale red or pink spots on the child's chest, thighs and other parts of the body; joint pain and inflammation. The rash may accompany the fever, and both may appear intermittently for many days in a row, while the joint pain and inflammation may accompany the fever or begin weeks or months later.
Joint problems can become a major long-term symptom. Other possible features of this form of arthritis include inflammation of the outer lining of the heart (pericarditis) or the lungs (leuritis); anemia and high white blood cells and platelets (cells that help with clotting); and enlarged lymph nodes, liver or spleen.
Because almost all children with this type of JRA test negative for both RF and ANA, blood work is usually done frequently in the first few weeks and months of this illness.
Approximately half of the children with systemic JRA recover significantly within one year of onset. However, flare-ups or a return of the illness can happen without warning or after some viral infections (mononucleosis and chicken pox, for example). In most children with systemic onset JRA, medications must be used for months to years to control the various aspects of the illness.
Long term problems due to systemic onset JRA are similar to polyarticular JRA. However, as uveitis is uncommon, the eyes only need to be checked yearly.

If systemic onset JRA is suspected, it is very important to have a correct diagnosis. Many children who have this illness have high fevers for at least part of every day. While feverish, the child looks very sick and doesn't want to be touched. However, when the child’s temperature becomes normal, he or she will look and feel better. It is important to note, also, that these children have a likelihood of developing bad reactions to medications and must be monitored very carefully.

Juvenile dermatomyositis (der-ma-toe-my-o-site-iss)
This is an inflammatory disease that causes muscle weakness and a characteristic skin rash on the eyelids.
Juvenile spondyloarthropathy (spon-duhlo-ar-throp-uh-thee)
This illness, accounting for less than 10 percent of JRA diagnoses, commonly affects teenage boys, causing arthritis in the hips, knees, or ankles. There may also be inflammation at the tendons where they connect to the bone, such as the Achilles tendon in the heel. The illness is often accompanied by acute inflammation of the eye .It may also develop into inflammation of the sacroiliac joints at the base of the spine. Ninety percent of children with spondyloarthropathy carry the HLA B27 antigen which can be detected by a blood test. Treatment is with NSAIDS and corticosteroid injections into the joints and DMARDs (explained in this website under Medications).

Juvenile systernis lupus erythematosus (er-uh-thee-muh-toe-sus)
This is an autoimmune disease associated with skin rashes, arthritis, pleurisy, kidney disease and neurologic movement.

Juvenile vasculitis (vask-u-light-us)
This is an inflammation of the blood vessels and can be both a primary childhood illness and a feature of other syndromes, including dermatomyositis and systemic lupus erythermatosus.
Ankylosing spondylitis
This is a form of joint inflammation that is long-lasting and most often affects the spine. It commonly causes pain and stiffness, with swelling and limited motion in the low back, middle back, neck, hips, chest wall, and heels.
Ankylosing spondylitis is a specific disease within a family of diseases called spondyloarthropathies. In severe cases the affected joints in the spine fuse together, causing severe stiffness in the back. Other joints can be stiff and painful, including those in the shoulders, wrists, hands, knees, ankles, and feet. Complications of ankylosing spondylitis may include inflammation of the colored part of the eye (iris), called iritis, or difficulty breathing due to curving of the upper body and stiffening of the chest wall. Inflammation from the condition may also affect the heart valves.
What causes juvenile rheumatoid arthritis?
JRA is an autoimmune disorder, which means that the body mistakenly identifies some of its own cells and tissues as foreign. The immune system, which normally helps to fight off harmful, foreign substances such as bacteria or viruses, begins to attack healthy cells and tissues. The result is inflammation, marked by redness, heat, pain, and swelling. Doctors do not know why the immune system goes awry in children who develop JRA. Scientists suspect that it is a two-step process. First, something in a child's genetic makeup gives him or her tendency to develop JRA; then an environmental factor, such as a virus, triggers the development of JRA.