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Juvenile Idiopathic Arthritis (JIA)
Juvenile idiopathic arthritis (JIA) is a group of rheumatic diseases that begins at or before age 16. Arthritis, fever, rash, adenopathy, splenomegaly, and iridocyclitis are typical of some forms. Diagnosis is clinical. Treatment involves NSAIDs, intra-articular corticosteroids, and disease-modifying antirheumatic drugs.
JIA is uncommon. The cause is unknown, but there seems to be a genetic predisposition and an autoimmune pathophysiology. JIA is distinct from adult RA (see Rheumatoid Arthritis (RA)), despite occasional similarities.
JIA is not a single disease; the term applies to a number of chronic arthritides that occur in children and share certain features. The current classification system, from the International League of Associations for Rheumatology, defines categories of disease based on clinical and laboratory findings. Some of the categories are subdivided into different forms. Categories include the following:
Many of these categories likely include more than one disease but are useful to help group children with a similar prognosis and response to treatment. Also, children sometimes move to different categories during the course of their illness.
Oligoarticular JIA is the most common form and usually affects young girls. It is characterized by involvement of ≤ 4 joints during the first 6 mo of disease. Oligoarticular JIA is further divided into 2 types: persistent (always ≤ 4 joints involved) and extended (≥ 5 joints involved after the first 6 mo of disease).
Polyarticular JIA is the second most common form. It affects ≥ 5 joints at onset and is divided into 2 types: RF negative and RF positive. Typically, young girls are RF negative and have a better prognosis. The RF-positive type typically occurs in adolescent girls and is often similar to adult RA. In both types, arthritis tends to be symmetric and frequently involves the small joints.
Enthesitis-related arthritis involves arthritis and enthesitis (painful inflammation at the insertion of tendons and ligaments). It is more common among older boys who may subsequently develop classic features of one of the spondyloarthropathies such as ankylosing spondylitis or reactive arthritis. The arthritis tends to be in the lower extremities and asymmetric. The HLA-B27 allele is more common in this form of JIA.
Psoriatic JIA typically occurs in young girls and is associated with psoriasis, dactylitis (swollen digits), nail pits, or a family history of psoriasis in a 1st-degree relative. Arthritis is frequently oligoarticular.
Undifferentiated JIA is diagnosed when patients do not meet criteria for any one category or meet criteria for more than one.
Systemic JIA (Still disease) is the least common form and involves fever and systemic manifestations.
Manifestations involve the joints and sometimes the eyes and/or skin; systemic JIA may affect multiple organs.
Children typically have joint stiffness, swelling, effusion, pain, and tenderness, but some children have no pain. Joint manifestations may be symmetric or asymmetric, and involve large or small joints. Enthesitis typically causes tenderness of the iliac crest and spine, greater trochanter of the femur, patella, tibial tuberosity, and Achilles and plantar fascia insertions.
Sometimes, JIA interferes with growth and development. Micrognathia (receded chin) due to early closure of mandibular epiphyses or limb length inequality (usually the affected limb is longer) may occur.
The most common ocular abnormality is iridocyclitis (inflammation of the anterior chamber and anterior vitreous―see see Uveitis Caused by Connective Tissue Disease : Juvenile idiopathic arthritis (JIA, previously known as juvenile RA)) that is typically asymptomatic but sometimes causes blurring of vision and miosis. Rarely, in enthesitis-related arthritis, there is conjunctival injection, pain, and photophobia. Iridocyclitis can result in scarring (synechia), glaucoma, or band keratopathy. Iridocyclitis is most common in oligoarticular JIA, developing in nearly 20% of patients, especially if patients are positive for antinuclear antibodies (ANA). It may occur in the other forms but is rare in polyarticular RF-positive JIA and systemic JIA.
Skin abnormalities are present mainly in psoriatic JIA, in which psoriatic skin lesions, dactylitis, and/or nail pits may be present, and in systemic JIA, in which a typical transient rash often appears with fever. Rash in systemic JIA may be diffuse and migratory, with urticarial or macular lesions with central clearing.
Systemic abnormalities in systemic JIA include high fever, rash, splenomegaly, generalized adenopathy (especially of the axillary nodes), and serositis with pericarditis or pleuritis. These symptoms may precede the development of arthritis. Fever occurs daily (quotidian) and is often highest in the afternoon or evening and may recur for weeks.
JIA should be suspected in children with symptoms of arthritis, signs of iridocyclitis, generalized adenopathy, splenomegaly, or unexplained rash or prolonged fever, especially if quotidian. Diagnosis is primarily clinical. Patients with JIA should be tested for RF, ANA, and HLA-B27 because these tests may be helpful in distinguishing between forms. In systemic JIA, RF and ANA are usually absent. In oligoarticular JIA, ANA are present in up to 75% of patients and RF is usually absent. In polyarticular JIA, RF usually is negative, but in some patients, mostly adolescent girls, it can be positive. HLA-B27 is present more commonly in enthesitis-related arthritis.
To diagnose iridocyclitis, a slit-lamp examination should be done even in the absence of ocular symptoms. A recently diagnosed patient with oligoarticular JIA should have an eye examination every 3 to 4 mo, and a patient with polyarticular JIA should have an eye examination every 6 mo.
Similar to the therapy of patients with adult RA, disease-modifying antirheumatic drugs (DMARDs), particularly methotrexate and the biologic agents (eg, etanercept, anakinra), have dramatically changed the therapeutic approach.
Symptoms may be reduced with NSAIDs but they do not alter long-term joint disease. NSAIDs are most useful for enthesitis. Naproxen 5 to 10 mg/kg po bid, ibuprofen 5 to 10 mg/kg po qid, and indomethacin 0.5 to 1.0 mg/kg po tid are among the most useful.
Except for severe systemic disease, systemic corticosteroids can usually be avoided. When necessary, the lowest possible dose is used (eg, range for oral prednisone, 0.0125 to 0.5 mg/kg qid, or the same daily dose given once or twice daily). Growth retardation, osteoporosis, and osteonecrosis are the major hazards of prolonged corticosteroid use in children. Intra-articular corticosteroid injections can be given. The dosage for children is adjusted based on weight. A few children may need to be sedated for intra-articular injection, especially if multiple joints require injection.
Methotrexate is useful for oligoarticular, psoriatic, and polyarticular forms of JIA. Adverse effects are monitored as in adults. Bone marrow depression and hepatic toxicity are monitored with CBC, AST, ALT, and albumin. Occasionally, sulfasalazine is used, especially in cases of suspected spondyloarthropathy.
Etanercept, used as in adults, blocks TNF-α and is often effective; 0.4 mg/kg sc (up to a maximum of 25 mg) is given twice/wk or 50 mg once/wk. Anakinra, which blocks the action of IL-1, is particularly effective in some patients with systemic JIA.
Physical therapy, exercises, splints, and other supportive measures may help prevent flexion contractures. Adaptive devices can improve function and minimize unnecessary stresses on inflamed joints. Iridocyclitis is treated with ophthalmic corticosteroid drops and mydriatics and may require systemic methotrexate and anti-TNF therapy (see Uveitis Caused by Connective Tissue Disease : Juvenile idiopathic arthritis (JIA, previously known as juvenile RA)).
JIA encompasses a number of different arthritides in children that differ in clinical and laboratory manifestations.
Suspect JIA in children with symptoms of arthritis, signs of iridocyclitis, generalized adenopathy, splenomegaly, or unexplained rash or prolonged fever.
Diagnose JIA clinically; use laboratory testing (eg, of RF, ANA, and HLA-B27) mainly to distinguish between forms.
Slow disease progression with methotrexate and/or biologic drugs (eg, etanercept, anakinra) and treat symptoms with intra-articular corticosteroid injections and/or NSAIDs.
Treat iridocyclitis with ophthalmic corticosteroid drops and mydriatics.
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