Oligoarticular Juvenile Idiopathic Arthritis

Oligoarticular JIA is defined by arthritis in four or fewer joints during the first 6 months of disease. Oligoarticular JIA is the most common form of JIA, typically occurs before age 4 years, and affects girls more often than boys at a ratio of 4 : 1. The knee is the most commonly affected joint followed by the ankles and small joints of the hand (Figure 26-1). The temporomandibular joint (TMJ) is also commonly affected. Children often experience morning stiffness, gelling (transient stiffness), and pain, but up to 25% may have painless arthritis. There are two subsets of oligoarthritis; persistent oligoarthritis affects a maximum of four joints throughout the disease course, and extended oligoarthritis affects more than four joints after the first 6 months of disease. Extended disease is associated with a worse prognosis.

Figure 26-1 Clinical signs of oligoarticular and polyarticular juvenile idiopathic arthritis.

Although children with oligoarticular JIA have the greatest likelihood of remission among the JIA subtypes, complications can cause long-lasting morbidities. Asymmetric joint disease (particularly at the knee) can lead to leg length discrepancy caused by hyperemia of inflammation. Severe disease of the TMJ can lead to difficulty chewing, malocclusion, or micrognathia. Asymptomatic iridocyclitis (anterior uveitis that affects the iris and ciliary body) is common in oligoarthritis, particularly among young girls who are ANA positive, and must be screened for at disease presentation and serially thereafter. Complications of uveitis include visual impairment, posterior synechiae, cataracts, band keratopathy, and glaucoma (Figure 26-2).

Figure 26-2 Ocular manifestations in juvenile idiopathic arthritis.

Polyarticular Juvenile Idiopathic Arthritis

Polyarticular JIA, defined by arthritis in five or more joints during the first 6 months of disease, is the second most frequent subtype of JIA. It is divided into two subtypes: RF-negative and RF-positive disease. Seronegative disease affects girls more frequently than boys. Seropositive patients are often adolescent girls who experience an insidious disease onset involving primarily the large and small joints of the hands and feet, the cervical spine, and TMJ. Rheumatoid nodules, boutonniere deformities (proximal interphalangeal joint flexion and distal interphalangeal joint hyperextension), and swan-neck deformities (proximal interphalangeal joint hyperextension and distal interphalangeal joint flexion) are frequently seen in seropositive patients. Mild systemic symptoms, such as low-grade fevers, lymphadenopathy, and hepatosplenomegaly, are common.

Systemic Juvenile Idiopathic Arthritis

Systemic JIA is defined by arthritis; fever for at least 2 weeks with high quotidian spikes for at least 3 days; and at least one of the following: evanescent and erythematous rash, lymphadenopathy, hepatosplenomegaly, and serositis (often pericarditis or pleuritis). The disease affects boys and girls equally and can occur at any age but most commonly in early childhood. Children often appear ill during fevers and appear well when afebrile. Arthritis is generally symmetric and polyarticular but may be absent at onset. The rash consists of discrete, salmon-pink macules that are more pronounced during fever and may be associated with the Koebner phenomenon (linear streaks on the skin elicited by scratching) (Figure 26-3).

Figure 26-3 Features of systemic juvenile idiopathic arthritis.

Complications of systemic JIA include macrophage-activating syndrome (MAS), systemic amyloidosis, infections caused by immunosuppression, and the effects of chronic corticosteroids. Approximately 5% to 8% of children with systemic JIA develop MAS. This life-threatening complication is characterized by acute onset of sustained fever, hepatosplenomegaly, and lymphadenopathy. Associated laboratory abnormalities may include pancytopenia, elevated fibrin split products, transaminitis, hypertriglyceridemia, hyperferritinemia, low erythrocyte sedimentation rate (ESR) (secondary to hypofibrinogenemia), and elevated coagulation factors. Bone marrow examination reveals active phagocytosis of hematopoietic cells.

Psoriatic Arthritis

Psoriatic arthritis is defined by presence of arthritis and psoriasis, or if the rash is absent, arthritis and at least two of the following: dactylitis, nail pitting or onycholysis, and psoriasis in a first-degree relative (Figure 26-4). The disease affects girls slightly more often than boys and has a bimodal onset, with peaks in the preschool years and early adolescence. The arthritis is usually an asymmetric monoarthritis or polyarthritis affecting large and small joints and may develop several years before the rash. Patients may be ANA positive and are at risk for developing uveitis.

Figure 26-4 Psoriatic juvenile idiopathic arthritis.

Enthesitis-Related Arthritis

Enthesitis-related arthritis (ERA) overlaps with spondyloarthropathies, juvenile ankylosing spondylitis (JAS), and inflammatory bowel disease (IBD)–associated arthritis. Enthesitis is inflammation around the enthesis, the insertion site of ligaments, tendons, joint capsule, or fascia to bones. This disease spectrum is defined by arthritis and enthesitis or either arthritis or enthesitis with at least two of the following: the presence or a history of sacroiliac tenderness or lumbosacral pain; HLA-B27 antigen positivity; onset of arthritis in a male after age 6 years; acute anterior uveitis; and a first-degree relative with ankylosing spondylitis, ERA, sacroiliitis with IBD, reactive arthritis, or acute anterior uveitis.

On physical examination, enthesitis is identified by tenderness where the tendons insert into the bones. Some common enthesitis sites include the inferior pole of the patella, Achilles tendon insertion, plantar fascia insertion, and sacroiliac joints. Progression to JAS is most likely among children with episodic arthritis of the lower extremity large joints, enthesitis, and tarsitis within 1 year of ERA symptom onset. Extraarticular manifestations of ERA include symptomatic anterior uveitis (red, painful, photophobic eye), aortic insufficiency, aortitis, muscle weakness, and low-grade fever. ERA can also be the initial manifestation of IBD (see Chapter 110). Thus, it is important to screen for gastrointestinal symptoms, growth failure, erythema nodosum, and aphthous stomatitis.

Undifferentiated Arthritis

Undifferentiated arthritis includes patients who do not meet criteria for any category or who meet criteria for more than one.

Pharmacologic Interventions

The purpose of pharmacologic therapy is to reduce pain, inflammation, and permanent joint destruction and to maintain remission. Nonsteroidal antiinflammatory drugs (NSAIDs), which have both analgesic and antiinflammatory properties, are often the initial intervention. However, most children with JIA require additional therapy. Intraarticular corticosteroid injections are often used to control disease locally, particularly in the setting of oligoarthritis. In children with polyarticular disease or oligoarticular disease that requires repeated intraarticular injections, disease-modifying antirheumatic agents and biologics are used. The most common of these medications include methotrexate, sulfasalazine, etanercept, infliximab, and adalimumab. Systemic corticosteroids are used for rapid control of severe arthritis and for children who have severe arthritis or systemic features that do not respond to other interventions. In cases of systemic JIA not adequately controlled with corticosteroids, biologic or chemotherapeutic agents may be used.

Surgical Management

Orthopaedic surgery has a limited role in the management plan for most children with JIA. However, in cases of refractory disease or persistent leg length discrepancy, an experienced orthopedic surgeon can help to design an individualized surgical intervention. Possible interventions include arthroscopic synovectomy, soft tissue release, epiphysiodesis (growth plate fusion), total arthroplasty (joint replacement), and arthrodesis (joint fusion).

Physical and Occupational Therapy

All children with prolonged arthritis should be evaluated by a physical or occupational therapist to maximize musculoskeletal health and function and to prevent flexion contractures. Among children with JIA, decreased physical activity, fitness, and function not only increase the risk of disability but also place these children at risk for long-term cardiovascular and obesity-related morbidity. Regular exercise programs will not exacerbate the disease and may even reduce disease symptoms. In cases of active joint disease in the upper extremities, occupational therapy can improve the capacity to perform activities of daily living and academic responsibilities.