Causes of Juvenile Rheumatoid Arthritis
An affliction of children under age 16, juvenile rheumatoid arthritis is an inflammatory disorder of the connective tissues characterized by joint swelling, pain, or tenderness. It may also involve organs such as the skin, heart, lungs, liver, spleen, and eyes, producing signs and symptoms other than those affecting movement.
Juvenile rheumatoid arthritis has three major types: systemic (Still's disease or acute feverish type), polyarticular, and pauciarticular. Depending on the type, this disease can occur as early as age 6 weeks (although rarely before 6 months) with peaks of onset between ages 1 and 3 and ages 8 and 12.
Considered the major chronic rheumatic disorder of childhood, this condition affects an estimated 150,000 to 250,000 children in the United States. Overall incidence is twice as high in girls, with variation among the types.
What causes it?
The cause of juvenile rheumatoid arthritis remains puzzling. Research continues to test several theories, such as those linking the condition to genetic factors or to an abnormal immune response. Viral or bacterial (particularly streptococcal) infection, trauma, and emotional stress may be precipitating factors, but their relationship to juvenile rheumatoid arthritis remains unclear.
What are its symptoms?
Signs and symptoms vary with the type of arthritis.
Systemic juvenile rheumatoid arthritis
Affecting boys and girls almost equally, the systemic disorder accounts for approximately 20% to 30% of cases. The affected children may have mild, transient arthritis or frank polyarthritis associated with fever and rash. Joint involvement may not be evident at first, but the child's behavior may clearly suggest joint pain. Such a child may want to constantly sit in a flexed position, may not walk much, or may refuse to walk at all. Young children with juvenile rheumatoid arthritis are noticeably irritable and listless.
Fever in systemic juvenile rheumatoid arthritis occurs suddenly and spikes to 103° F (39.4° C) or higher, once or twice daily, usually in the late afternoon, and then rapidly returns to normal or subnormal. (This "sawtooth" or intermittent spiking fever pattern helps distinguish juvenile rheumatoid arthritis from other inflammatory disorders.)
When fever spikes, a transient rheumatoid rash often appears, consisting of small, pale, or salmon-pink macules, most commonly on the trunk and proximal extremities and, occasionally, on the face, palms, and soles. Massaging or applying heat intensifies this rash, which is usually most conspicuous where the skin has been rubbed or subjected to pressure, such as from tight-fitting underclothing.
Other signs and symptoms of the systemic type may include an enlarged liver and spleen, disease of the lymph nodes, pleuritis, pericarditis, myocarditis, and nonspecific abdominal pain.
Polyarticular juvenile rheumatoid arthritis
This type affects girls three times more often than boys and may be seronegative or seropositive for rheumatoid factor. It involves five or more joints and usually develops insidiously. Most commonly involved joints are the wrists, elbows, knees, ankles, and small joints of the hands and feet. The polyarticular type can also affect larger joints. including the temporomandibular joints and those of the cervical spine, hips, and shoulders. These joints become swollen, tender, and stiff. Usually, the arthritis affects both sides; it may come and go or cause little discomfort. The person may run a low-grade fever with daily peaks. Listlessness and weight loss also can occur, possibly with enlarged lymph nodes, liver, and spleen. Other signs of the polyarticular type include lumps under the skin of the elbows or heels and noticeable developmental retardation.
Seropositive polyarticular juvenile rheumatoid arthritis, the most severe type, usually occurs late in childhood and can cause destructive arthritis that mimics adult rheumatoid arthritis.
Pauciarticular juvenile rheumatoid arthritis
This type involves few joints (usually no more than four) and most often affects the knees and other large joints. It accounts for 45% or' cases. Three major subtypes exist:
The first type, pauciarticular juvenile rheumatoid arthritis with chronic iridocyclitis, most commonly strikes girls under age 6 and involves the knees, elbows, ankles, or iris. Inflammation of the iris ane ciliary body is often without symptoms but may produce pain, redness, blurred vision, and sensitivity to light.
The second subtype, pauciarticular juvenile rheumatoid arthrirtis with sacroiliitis, usually strikes boys over age 8, who tend to be positive for human leukocyte antigen B27. This subtype is characterizec by lower extremity arthritis that produces hip, sacroiliac, heel, ane foot pain and Achilles tendinitis. These children may later develo? the sacroiliac and lumbar arthritis characteristic of ankylosing spondylitis. Some also experience acute iritis, but not as frequently as those with the first subtype.
The third subtype includes people with joint involvement who are negative for antinuclear antibody and human leukocyte antigen B27 and do not develop iritis. These people have a better prognosis than, those with the first or second subtype.
Common to all types of juvenile rheumatoid arthritis is joint stiffness in the morning or after periods of inactivity. Growth disturbances may also occur, resulting in overgrowth or undergrowth adjacent to inflamed joints.
How is it diagnosed?
Persistent joint pain and the rash and fever clearly point to juvenile rheumatoid arthritis. Lab tests are useful for ruling out other inflammatory or even malignant diseases that can mimic the condition and for monitoring disease activity and response to therapy.
How is it treated?
Successful management of juvenile rheumatoid arthritis usually involves administration of anti-inflammatory drugs, physical therapy, carefully planned nutrition and exercise, and regular eye exams. Both child and parents must be involved in therapy.
Aspirin is the initial drug of choice, with dosage based on the child's weight. However, other nonsteroidal anti-inflammatory drugs may also be used. If these prove ineffective, gold salts, Plaquenil, and Cuprimine may be tried. Because of side effects, corticosteroids are generally reserved for treatment of systemic complications, such as pericarditis or iritis, that are resistant to nonsteroidal anti-inflammatory drugs. Corticosteroids and mydriatic drugs are commonly used for iridocyclitis. Low-dose cytotoxic drug therapy is currently being investigated.
Physical therapy promotes regular exercise to maintain joint mobility and muscle strength, thereby preventing contractures, deformity, and disability. Good posture, gait training, and joint protection are also beneficial. Splints help reduce pain, prevent contractures, and maintain correct joint alignment .
Regular slit-lamp examinations help ensure early diagnosis and treatment of iridocyclitis. Children with pauciarticular juvenile rheumatoid arthritis with chronic iridocyclitis should be checked every 3 months during periods of active disease and every 6 months during remissions.
Generally, the prognosis for juvenile rheumatoid arthritis is good, although disabilities can occur. Surgery is usually limited to soft-tissue releases to improve joint mobility. Joint replacement is delayed until the child has matured physically and can handle vigorous rehabilitation.
Parents and health care professionals should encourage the child to be as independent as possible and to develop a positive attitude toward school, social development, and vocational planning.
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