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The word spondyloarthropathy (referring to arthritis
of the spine and sacroiliac joints) evolved in the adult population
to distinguish a group of chronic arthritides that differed from
rheumatoid arthritis. These conditions were distinct in that they
involved axial joints, were associated with the HLA-B27 haplotype,
had a frequent family history of these diseases, and were rheumatoid
factor negative. Traditionally the specifically named spondyloarthropathies
included ankylosing spondylitis, psoriatic arthritis, the arthropathy
of inflammatory bowel disease, and Reiter disease.
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This characterization has not been entirely satisfactory, because
many patients do not comfortably fit into one of these explicitly
defined categories.1-3 The efficacy of current
pharmacotherapy for AS has driven the development of clinical algorithms
(judiciously using magnetic resonance imaging [MRI])
to identify early disease and thereby allowing initiation of appropriate
therapy before the development of irreversible damage.4,5
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A major deficiency of the earlier classification systems for
pediatric chronic arthritis was the failure to adequately distinguish
children with arthritis who have, or who might ultimately develop,
a spondyloarthropathy, from those with juvenile rheumatoid arthritis.6-8 Although the
EULAR classification includes juvenile ankylosing spondylitis and
juvenile psoriatic arthritis, these conditions are defined according
to adult criteria that require the presence of radiologically identified
sacroiliitis or psoriasis, respectively. Children who ultimately
develop ankylosing spondylitis (AS), however, will generally not
present with back pain or sacroiliitis (the primary requisites for
diagnosing AS in adults). Rather, they typically have peripheral
arthritis and a constellation of other features including enthesitis,
onset later in childhood, a family history of AS or related diseases,
and presence of HLA-B27 antigen.9,10 To address
these deficiencies, such patients have been variously described
as having the syndrome of seronegative enthesopathy and arthropathy
(SEA syndrome), pauciarticular onset juvenile rheumatoid arthritis
(JRA) type II, late-onset pauciarticular juvenile chronic arthritis
(LOPA), and HLA-B27-associated arthropathy and enthesopathy syndrome.11-14 Patients
with these various syndromes could also be characterized as having “early” or “undifferentiated” spondyloarthropathy.
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The evolution of nomenclature within the International League
of Associations for Rheumatology (ILAR) system for classifying pediatric chronic
arthritis has encapsulated all of these syndromes in the category
of enthesitis-related arthritis (ERA) (see Chapter 201).15Enthesitis, the
most common defining clinical feature of these syndromes, refers
to inflammation (pain, tenderness, and swelling) of the enthesis,
the site of attachment of tendon, ligament, or fascia to bone. Thus,
children with juvenile ankylosing spondylitis (JAS) also fulfill
criteria for ERA. As will be discussed under the section of this
chapter, “Juvenile Psoriatic Arthritis,” children
with arthritis and either psoriasis or psoriatic features probably
do not represent a homogeneous subset of childhood arthritis despite
their current classification within spondyloarthropathies (see Table 202-1). Children with inflammatory
bowel disease associated arthritis or Reiter disease may or may
not develop axial arthritis and these conditions will also be discussed
below.
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