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Juvenile rheumatoid arthritis is a chronic inflammatory disease that always involves the joints, but may produce extensive connective tissue and visceral lesions. Despite extensive research the etiology of JRA remains unclear. No autoantibody specific for the disease has been documented. Much evidence points to a major role for immunologic reactivity in perpetuating rheumatoid inflammation.

Unidentified initiating factors probably stimulate a synovitis that triggers the local synthesis if IgG and rheumatoid factor (IgM anti- IgG) by plasma cells within the joint. Activation of the complement system within the joint space generates several materials that attract PMN’s into the joint cavity, where they phagocytize the immune complex, thus leading to the formation of the rheumatoid arthritis cells. The neutrophils, following phagocytosis, are stimulated to discharge hydrolase from lysosomal granules. These enzymes together with fibrinogen may initiate the destructive changes characteristic of rheumatoid joint disease.

JRA is arbitrarily defined as beginning before the age of 16 years. It is slightly more common in females than in males and is said to affect as many as 250,000 children in the United States. Although JRA may begin at any age, an increased incidence of onset generally occurs from 1- 3 years of age and later from 8- 12 years of age. Approximately 20% have acute systemic JRA which is characterized by febrile onset, variable joint manifestations, rash, generalized lymphadenopathy, splenomegaly, liver disease, and rarely by GI tract disease.

Other children with JRA primarily have arthritis that is present at the onset of illness. In 30% only a single joint, usually the knee is involved; in 50% multiple joints are involved. The disease is termed polyarticular if more than 4 joints are involved and pauciarticular if fewer than 4 joints are affected.

Pauciarticular juvenile rheumatoid arthritis falls into 2 distinct categories. In 1 group, involving females between the ages of 1- 4 years, onset of the joint involvement occurs in the knees, ankles, or elbows. The small joints of the hands are spared. Painless swelling of the involved joint is common. A positive speckled antinuclear antibody is frequently found. Although fatigue and low grade fevers are occasionally seen, the only significant systemic manifestation is iridocyclitis, which may occur in 25% of these children. Eye disease can be present without eye pain, redness, or other clinical signs. Slit lamp examination is imperative in these children. A chronic, non- granulomatous inflammation of the uveal tract involves predominantly the anterior segments of the eye, iris, and ciliary body. The earliest signs of uveitis are those of cellular exudate and an increased number of inflammatory cells in the anterior chamber of the eye. Inadequately controlled inflammation will lead to progressive damage, with the development of posterior synechiae that arise from adherence of the iris to the anterior surface of the lens and result in an irregular or poorly reactive pupil.

The second form of pauciarticular arthritis occurs in predominantly in boys 8 years of age or older. Family histories are often positive for Reiter reactive arthritis or ankylosing spondylitis. Large joints, particularly those of the lower extremity, are involved. Hip- girdle involvement often occurs at the onset of the disease and with time, sacroiliitis may be demonstrated by x- ray in approximately 90% of this group. About 95% of patients with ankylosing spondylitis are HLA B27 positive. Tests for rheumatoid factor and antinuclear antibody are negative. Chronic iridocyclitis is not associated with this form of the disease although self- limited iritis may occur in 20%.

Ankylosing spondylitis is characterized by an inflammatory involvement of the large joints of the limbs and spine. The entire spine may be involved along the sacroiliac, hip, shoulder, knee, ankle, and costovertebral joints. The disease affects males primarily, with 10% beginning before 15 years of age. There is a high association with HLA B27. Ankylosing spondylitis may be associated with an acute iridocyclitis.

Rheumatoid factor is rarely positive in children with JRA, except in the pauciarticular form, where it may be positive in up to 15% of patients. Antinuclear antibody may be positive, if so, it is often in a speckled pattern. A positive ANA is found in young females with pauciarticular arthritis who are at risk for developing iridocyclitis.

The differential diagnosis includes acute and chronic infection, malignancy, postrubella immunization arthritis, Kawasaki’s disease, inflammatory bowel disease, rheumatic fever, ANAPHYLACTOID PURPURA, SLE, and acute arthritis associated with shigella or yersinia infections.

Aspirin is the preferred drug for therapy given as 80- 100mg/kg/day. The more frequent and higher doses are usually reserved for children with more severe disease. Serum salicylate levels should be maintained between 20 and 30mg/dl. Liver enzymes should be monitored prior to and during aspirin therapy. Some elevation of liver enzymes almost always occurs. Treatment, in the absence of overt side effects, should be continued for 6 months beyond any indication of active disease and therapy should be tapered slowly. Prednisone in a dose of 1mg/kg/day may be used for brief periods. Two indications for immediate Prednisone therapy are carditis or Coomb- positive hemolytic anemia. Physical therapy of the involved joints is essential in preventing long- term disability. Other therapies involve the use of nonsteroidal anti- inflammatory agents, gold salts, and indomethacin. Indomethacin is frequently more effective in treating individuals with pauciarticular arthritis of the lower extremities and ankylosing spondylitis. The recommended dose is 1.5 - 3mg/k/day and should not exceed 250mg/day.

If a child with pauciarticular JRA does not develop eye disease, has well controlled joint disease, and has maintained full ROM with vigorous physical therapy, then by age 20 years the disease generally becomes quiescent. In children with chronic uveitis approximately 60% have complete recovery or normal sight, 25% have impaired vision or unilateral blindness, and approximately 10% are blind.