What Causes Juvenile Rheumatoid Arthritis?

Although a specific trigger has not been identified, T lymphocytes of genetically predisposed children are chronically activated to recruit other inflammatory cells, leading to synovitis. The prevalence of juvenile rheumatoid arthritis (JRA) is about 1.3 in 1000 children in the general population.

What Is the Typical Clinical Presentation of Juvenile Rheumatoid Arthritis?

All cases of JRA are characterized by chronic arthritis (joint pain, limitation of range of motion, joint swelling, and/or warmth) for at least 6 weeks without another etiology such as Lyme disease. Morning stiffness is common, but severe pain, especially at night, should raise concerns about another diagnosis such as leukemia. There are three general presentations for JRA based on clinical findings during the first 6 months of disease.

What Laboratory Tests Should I Order?

Complete blood count (CBC) may reveal anemia of chronic disease or iron-deficiency anemia from gastrointestinal blood loss caused by nonsteroidal antiinflammatory drugs (NSAIDs). The erythrocyte sedimentation rate (ESR) is often elevated. Antinuclear antibody (ANA) and the rheumatoid factor (RF) may be variably positive, as indicated in Table 70-1. Patients on NSAIDs are monitored for liver toxicity by checking liver enzymes and for renal dysfunction by periodically checking a urinalysis.

Table 70-1 Findings and Prognosis in Rheumatoid Arthritis

Do Laboratory Test Results Predict Disease and Prognosis?

In general, patients with positive ANA have a better prognosis than those with positive RF. Overall, however, clinical signs and symptoms are the best indicators of prognosis and disease control rather than lab tests. Joint destruction and unremitting disease progressing into adulthood are most common in patients who are positive for RF.

How Is Rheumatoid Arthritis Treated?

The mainstays of treatment are the NSAIDs. Disease-modifying drugs such as methotrexate and biologic therapies are reserved for those with persistent symptoms and radiologic evidence of erosions. Etanercept, a recombinant anti-TNF, has proven efficacy for patients with moderate to severe polyarticular JRA unresponsive to NSAIDs or methotrexate but is associated with an increased risk of infection. Sulfasalazine is also being used to treat patients with unresponsive JRA but has been associated with a risk of severe hypersensitivity reactions, such as Stevens-Johnson syndrome. Corticosteroids may be used systemically to quiet the inflammation seen in systemic-onset JRA. Chronic use of steroids should be minimized to avoid side effects. Steroids are also used in joint injections or topically as ophthalmic drops to treat uveitis. One of the primary concerns with long-term steroid use is poor bone mineralization during treatment. Various agents such as alendronate are being studying to help ameliorate osteopenia resulting from long-term steroid use, but their role in management of JRA is not yet clear.

What Is the Cause of Systemic Lupus Erythematosus?

A single etiologic agent cannot explain systemic lupus erythematosus (SLE), a complex autoimmune disorder involving autoantibodies to a variety of tissues throughout the body. It is thought that a combination of hormones and environmental stimuli activate B lymphocytes in genetically predisposed individuals, triggering production of autoantibodies. Disease prevalence varies between 4 and 250 cases per 100,000 children, depending on gender and ethnicity. SLE is more common among Native American, Asian, Latino, and African-American children than in white patients. Girls are four times more likely to develop SLE than are boys before puberty and eight times more likely afterward.

How Do Patients with Systemic Lupus Erythematosus Present?

Most of the physical findings in SLE result from vasculitis. SLE can present at any age from the newborn period into adult life. The typical patient with SLE is an African-American adolescent girl with weight loss, fatigue, arthralgias, and rash, all of which often are induced by sun exposure. Over the course of the illness, 80% develop glomerulonephritis. Neonatal lupus manifests as rash and heart block in a newborn infant, resulting from placental transfer of autoantibodies from a mother with the disease. Outside of the neonatal period, SLE is uncommon in males and in children younger than 10 years. SLE should be considered in the differential diagnosis when children or adolescents present acutely with unusual findings, such as thrombosis, psychosis, or pericardial or pleural effusions (serositis). Table 70-2 depicts the most common multiorgan system findings in SLE. Diagnosis is based on the combination of clinical findings plus laboratory test results. To categorize patients as having SLE for clinical research studies, 4 of the 11 findings in Table 70-2 must be present. In clinical practice, the diagnosis is often made with fewer than four findings.

Table 70-2 1982 Revised Criteria for Diagnosis of Systemic Lupus Erythematosus

What Laboratory Tests Help to Diagnose and Monitor Systemic Lupus Erythematosus?

No single laboratory test can be used to diagnose SLE. In addition to nonspecific findings of inflammation, such as an elevated ESR, several autoantibodies may be found. The ANA has high sensitivity but low specificity for SLE. Anti-SSA and anti-SSB antibodies occur more often with Sjögren’s syndrome than with SLE. Anti-Smith antibody is specific for SLE but is not an indicator of disease activity. Anti–double-stranded DNA is specific for SLE and reflects disease activity, although decreased levels of complement (CH50, C3, C4) are better markers of disease activity. Autoantibodies can cause a range of laboratory and clinical abnormalities, depending on the organ system affected. All of the cell lines on the CBC can be depressed because of antibodies produced against white blood cells (ANA), red blood cells (Coombs’), or platelets. Other autoantibodies can be associated with hypothyroidism (antithyroid antibodies), cerebritis (antiribosomal P antibody), and coagulopathy or thrombosis (lupus anticoagulant/antiphospholipid antibodies). Elevations in transaminases reflect autoimmune hepatitis. Hematuria and proteinuria as seen on urinalysis reflect renal disease.