Juvenile idiopathic arthritis (JIA) is a diverse spectrum of chronic arthritides, involving arthritis of at least one joint for 6 or more wk in patients 15 yr of age or younger. Other causes of arthritis must be excluded.

Juvenile idiopathic arthritis (JIA)

Oligoarticular JIA

Polyarticular JIA

Juvenile psoriatic arthritis

Enthesitis-related arthritis

Systemic JIA

JIA is thought to have a global distribution. While the exact incidence and prevalence are unknown, incidence rates pooled from predominantly North American and European studies are approximately 8 per 1000 children. The predominant sex and age of patients with JIA varies by JIA subtype. The precise immunopathogenic mechanism underlying the development of disease has not been elucidated, but genetic susceptibility, environmental influences, and lifestyle modifications are all hypothesized to play a role.¹

• JIA is subdivided into seven categories based on the International League of Associations for Rheumatology (ILAR) classification criteria (summarized in Table E1), all of which require the presence of chronic arthritis (arthritis for ≥6 wk). Characteristics of the various categories of JIA are summarized in Table E2
• Oligoarticular JIA (Fig. E1)
• Arthritis in ≤4 joints in the first 6 mo of disease
  1. There are two subtypes:
     1. Persistent: ≤4 joints throughout the disease course
     2. Extended: ≤4 joints during the first 6 mo, extending to >4 joints after 6 months
• Polyarticular JIA rheumatoid factor (RF)-negative polyarticular JIA
  1. Arthritis in ≥5 joints during the first 6 mo of the disease, with negative RF
• RF-positive polyarticular JIA
  1. Arthritis in ≥5 joints during the first 6 mo of disease, with positive RF on ≥2 tests (run 3 mo apart). Anticyclic citrullinated (CCP) antibodies are positive in about 60% of patients.
• Psoriatic arthritis
  1. Psoriasis and arthritis, OR arthritis and ≥2 of the following:
     1. Dactylitis
     2. Nail pitting or onycholysis
     3. Psoriasis in a first-degree relative
• Enthesitis-related arthritis
  1. Enthesitis refers to inflammation at the sites where ligaments, tendons, fascia, or capsules attach to the bone
  2. Arthritis and enthesitis, OR arthritis or enthesitis plus ≥2 of the following:
     1. Sacroiliac tenderness
     2. Positive HLA-B27
     3. Male age >6 yr
     4. Acute anterior uveitis
     5. First-degree relative with HLA-B27-associated disease
• Undifferentiated arthritis
  1. Fulfills criteria in ≥2 categories above, or none of them
  2. Systemic JIA (sJIA)
     1. Arthritis in ≥1 joints with, or preceded by, fever (Fig. E2) of at least 2-wk duration that is quotidian (once daily) for at least 3 days and associated with at least one of the following: (1) Evanescent rash (Fig. E3); (2) generalized lymphadenopathy; (3) hepatomegaly, splenomegaly, or both; and (4) serositis.

Genetically susceptible individuals may develop an inappropriate immune response toward a self-antigen after exposure to an environmental trigger. Variants in HLA, PTPN22, and STAT4 loci may be associated with disease.

• Table E3 summarizes the differential diagnosis of pediatric arthritis syndromes.

• JIA is a clinical diagnosis; there is no single diagnostic test.
• In some subtypes, there are signs of systemic inflammation (elevated sedimentation rate and C-reactive protein; high ferritin; anemia of chronic disease; leukocytosis).
• Rheumatoid factor (RF) and anticyclic citrullinated peptide (CCP) antibodies can be seen in polyarticular JIA.
• A positive antinuclear antibody (ANA) test is associated with uveitis.
• Pancytopenia, a consumptive coagulopathy, elevated ferritin, and elevated liver enzymes are concerning for macrophage activation syndrome (MAS), a possible complication of systemic JIA.

• Imaging is not necessary for the diagnosis of JIA.
• Radiographs are often normal, but they can show effusions and periarticular osteopenia.
• Joint destruction, as evidenced by bony erosion and cyst formation, may be present and is more common in RF/CCP-positive disease.

Collaboration among the patient’s pediatrician, rheumatologist, and physical therapist is essential.

• Nonsteroidal antiinflammatory drugs (NSAIDs)
• Intraarticular corticosteroids
• Disease modifying antirheumatic drugs (DMARDs):
  1. Conventional DMARDs:
     1. Methotrexate, leflunomide, sulfasalazine
  2. Targeted synthetic DMARDs:
     1. Janus kinase (JAK) inhibitors (such as tofacitinib and ruxolitinib)
• Biologics:
  1. Tumor necrosis factor (TNF)-alpha inhibitors (such as adalimumab and etanercept)
  2. T-cell modulators (such as abatacept)
  3. B-cell agents (such as rituximab)
  4. Interleukin (IL) inhibitors (anakinra, canakinumab, tocilizumab, secukinumab, ustekinumab)
• Systemic corticosteroids should be limited when possible.
• Major medications and indications for the treatment of JIA are summarized in Table E4.

• Nearly 90% of patients with JIA achieve clinically inactive disease, but more than 50% continue to require medication to control their disease 10 yr after diagnosis.²
• Patients with persistent oligoarticular disease are most likely to achieve remission, while those who have RF-positive polyarticular disease are least likely to achieve remission.
• Macrophage activation syndrome is a life-threatening complication of sJIA.³

• Early rheumatology consultation
• Ophthalmology consultation at diagnosis and every 3 to 12 mo depending on risk for uveitis
  1. Children <7 yr old with a positive ANA are at the highest risk for uveitis.⁴

JIA is an autoimmune disease with a complex etiology, including genetic, environmental, and immune system influences. In the absence of treatment, patients are at risk of leg-length discrepancy, muscle atrophy, joint contractures, joint destruction, and micrognathia. Immunomodulators have significantly reduced disease progression and allow the vast majority of patients to achieve disease remission.

Juvenile Idiopathic Arthritis (Patient Information)