Chapter 202

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.

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

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.

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.

Table 202-1. Comparison of Psoriatic Arthritis, Oligoarthritis, Enthesitis-Related Arthritis, and Juvenile ...

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