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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.
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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.
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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
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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.
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Clinical Presentations
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