Chapter 204

Systemic lupus erythematosus (SLE) represents the prototype of a pediatric autoimmune disease with the presence of autoantibodies as its hallmark. The incidence of SLE diagnosed prior to age 18 is approximately 10 to 20 new cases per 100,000 population per year with an overall prevalence of 1 to 2 cases per 1000 adolescents ages 12 to 18. Both the incidence and prevalence rates are higher in African Americans, Asians, Southeast Asians, and Hispanics. The female predominance (4–4.5:1) in pediatric patients is lower than in adults (9:1).1 The mean age at diagnosis is approximately 12 to 13 years, but presentation as young as age 3 or 4 is routinely reported.2 Presentation prior to age 1 is very rare and may manifest as congenital nephrotic syndrome.

Neonatal lupus erythematosus (NLE) must not be mistaken for early-onset SLE. NLE is a disease caused by the transplacental passage of maternal autoantibodies, and the fetus/neonate is an innocent bystander with a normal immune system that is not actively producing autoantibodies. However, some of these children may develop true SLE many years later. Early-onset pediatric SLE is a disease in which the child produces autoantibodies and the immune abnormalities are intrinsic to the child’s immune system.

### Etiology

Although the triggering mechanisms are not fully defined, the production of autoantibodies is the hallmark of SLE. These autoantibodies are usually directed against histone, nonhistone, RNA-binding, cytoplasmic, and nuclear proteins. Antinuclear antibody (ANA) occurs in most, if not all, patients with SLE. With more sensitive detection systems, ANA-negative SLE is very rare but still does occur (<5% of cases). Anti-DNA antibodies are present in approximately 50% to 60% of patients, while antibodies directed against the small nuclear ribonuclear proteins (anti-Sm and anti-70kDa RNP antibodies) occur in 40% to 50% of patients.3 Antibodies directed against small cytoplasmic ribonuclear proteins (anti-Ro and/or anti-La antibodies) occur in 30% to 40% of patients, anticardiolipin antibodies in 40% to 50% of patients, and rheumatoid factor 15% to 20% of patients. Antiribosomal P antibodies are present in approximately 25% to 30% of patients and may be associated with psychosis and depression.4,5

Antiphospholipid and anticardiolipin antibodies are detected in approximately 50% of patients.6 One specific antiphopholipid antibody worth noting is the lupus anticoagulant (LAC), an antibody that reacts with phospholipids in the reagent used in the partial thromboplastin time (PTT) determination. The LAC is often seen in conjunction with anticardiolipin antibodies. Patients with LAC do not bleed; instead, they have an increased incidence of deep vein thrombosis, thromboemboli, or, less commonly, arterial thrombosis. Antiphospholipid antibodies are associated with multiple neurologic manifestations including stroke, seizures, chorea, and other movement disorders; pseudotumor cerebri; and migraine headache; as well as with nonneurologic disorders such as thrombosis, thrombocytopenia, or recurrent abortion.6–9 Most, if not all, pediatric patients with evidence of venous thromboembolic disease will have evidence of LAC.

### Clinical Presentations

In 1997 the American College of Rheumatology (ACR) revised the criteria for classification of SLE (Table 204-1).10 These criteria were not to be used to diagnosis and separate SLE patients ...

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