Juvenile idiopathic arthritis: current and future therapies.
Abstract: Juvenile idiopathic arthritis (JIA) consists of a group of heterogeneous disorders of chronic arthritis in childhood with no apparent cause. JIA is the most common rheumatic disease in children and may still result in significant morbidity, with joint deformity, growth impairment, and persistence of active arthritis into adulthood. In addition to arthritis, the extra-articular features that may be present in JIA, such as anterior uveitis or the fever of systemic-onset JIA, are often the greater focus of therapy. Prior to the mid 1990s, the therapeutic armamentarium for JIA was more limited, utilizing nonspecific agents, many with significant adverse effects. In the new era of target-specific biologic therapy, the clinician is now able to better tailor therapy for patients with JIA. Still, despite the bells and whistles of biologics, the consistent performance of methotrexate as the gold standard disease-modifying anti-rheumatic drug (DMARD), against which all other agents are compared, cannot be overemphasized. Through continued translational research, rheumatologists better understand the biology behind the clinical symptoms. This review will discuss the clinical features of JIA, as well as past, present, and future therapeutic approaches in the care of children with arthritis.
Subject: Methotrexate (Health aspects)
Arthritis (Health aspects)
Children (Diseases)
Children (Health aspects)
Author: Kahn, Philip
Pub Date: 07/01/2009
Publication: Name: Bulletin of the NYU Hospital for Joint Diseases Publisher: J. Michael Ryan Publishing Co. Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 J. Michael Ryan Publishing Co. ISSN: 1936-9719
Issue: Date: July, 2009 Source Volume: 67 Source Issue: 3
Accession Number: 247340118
Full Text: Childhood chronic arthritis of unknown etiology is now known collectively as juvenile idiopathic arthritis (JIA), according to the International League of Associations for Rheumatology (ILAR). (1,2) JIA is the most common rheumatic disease in children, (3,4) and consists of eight heterogeneous subsets with unique clinical patterns of disease (Table 1). The primary aim for the reclassification of JIA was to define relatively homogeneous, mutually exclusive subsets of arthritis, based on predominant clinical and laboratory features, for both prognostic and research purposes. JIA has replaced former nomenclature, including the term juvenile rheumatoid arthritis (JRA) in the United States and juvenile chronic arthritis (JCA) internationally. In addition, there is also the awareness that only 10% of childhood arthritis may be characterized as "rheumatoid," with a similar clinical phenotype to adult rheumatoid arthritis (RA).

The subtypes that have been recognized previously as JRA are classified based on clinical presentation during the first 6 months of disease, categorizing patients as oligoarticular, polyarticular, or systemic-onset JIA--these subsets representing the focus of this article. The newer JIA classification has expanded further the former JRA classification to include other helpful subclassifications, such as extended oligoarticular JIA, psoriatic arthritis, enthesitis-related arthritis, and undifferentiated arthritis. Enthesitis-related arthritis, a.k.a. spondyloarthropathies, includes patients with ankylosing spondylitis, reactive arthritis, and the arthritis of inflammatory bowel disease. Undifferentiated arthritis pertains to patients who do not fulfill criteria for other subclassifications or fulfill more than one. Common to all subclassifications of JIA is the onset of arthritis prior to age 17, which persists for at least 6 weeks in duration and is etiologically idiopathic.

As with most classification criteria in rheumatology, the diagnosis of JIA is one of exclusion, obligating the clinician to rule out other causes of chronic arthritis, including rheumatic, infectious, and other definable etiologies. The original classification of JIA has been revised several times, most recently in 2004, resulting in further clarification of the various subsets, correction of prior incongruence, and improvement in clinical utility to the rheumatologist. (5)

Epidemiology

Although the JIA estimated incidence is one out of every 1000 children worldwide, the exact statistic regarding this frequency is challenging, largely, but not solely, due to the lack of awareness and aptitude among pediatricians in diagnosing this syndrome. Nevertheless, it is believed that there are over 300,000 children with JIA in the U.S. Similar to most rheumatic disease, twice as many females than males may develop JIA, mainly reflecting the female predominance of oligoarticular JIA, the most prevalent subgroup. Unlike other rheumatic disease, there is no racial predilection for JIA. Although certain subsets have an age-specific peak incidence, it is very unusual for children to develop JIA before 6 months of age, similar to the epidemiology of most other rheumatic diseases. It is not uncommon to discover a family history of autoimmune disease in children with JIA.

Research Approaches in JIA

Conducting randomized, placebo-controlled trials in children with JIA has been challenging, especially as it pertains to medication with demonstrable benefit in adult RA. In order to enable the collection of invaluable data regarding medications taken by children with JIA, the majority of these clinical drug trials in JIA use the withdrawal study design, exemplified by the etanercept trial in JIA in 1999. (6) This study was the result of the successful collaborative efforts of the Pediatric Rheumatology Collaborative Study Group (PRCSG), consisting of an international group of pediatric rheumatologists, who have unified to study uncommon rheumatic diseases of childhood. Other consortiums that have made these clinical trials possible include the Childhood Arthritis and Rheumatology Research Alliance (CARRA) and the Pediatric Rheumatology International Trials Organization (PRINTO). Prior to the etanercept withdrawal trial design through PRCSG, much of the treatment of JIA was based on the adult RA literature, as well as a few placebocontrolled trials, case series, open-label trials, or anecdotal studies in pediatric rheumatology not designed within the parameters of evidence-based medicine. JIA outcome measures have been validated and are now widely used in clinical trials, including the American College of Rheumatology (ACR) Pedi 30/50/70 (Table 2).

General Treatment Aspects

Although various therapeutic algorithms have been published regarding the treatment of children with chronic arthritis, there are no widely accepted protocols. (7,8) Overall, the clinician seeks to eliminate all signs and symptoms of active disease, in order to preserve normal joint function and prevent deformity and disability. As JIA is a chronic, potentially lifelong disease, many children are exposed to the consequences of prolonged inflammation, as well as to the adverse reactions of long-term medications. It is essential that every attempt is made to preserve normal physical and psychosocial development of children with arthritis, using a multidisciplinary, holistic approach to the child with a chronic illness, and avoid the "sick role."

A potential barrier in the care of children with chronic disease is patient noncompliance, especially in the adolescent patient. The early establishment of nonjudgmental and open communication, as well as including the teenage patient in making age-appropriate therapeutic decisions, may help avoid this situation.

Unlike a typical adult RA patient who has other coexisting disease, children with JIA have less comorbidity, and, therefore, may better tolerate medications. This may explain the superior tolerability of medications in JIA, such as methotrexate, in contrast to adult RA patients, although there are limited safety studies regarding these pharmacologic agents. Unlike adult RA outcome measures, the evaluation of "permanent" damage may be inappropriate in JIA, as the growing child may recover from lesions deemed permanent in adult RA, such as avascular necrosis or bone erosion.

Clinical Presentation (Typical Scenarios)

Oligoarticular JIA

Oligoarticular JIA (Oligo-JIA) is the most common subset, accounting for 50% to 60% of JIA; 80% of patients are female, with a peak age of onset between 1 and 3 years of age. By definition, the patient presents with arthritis of four or fewer joints during the first 6 months of disease onset. Knees and ankles are most commonly affected, and, at presentation, 50% of patients have a monoarthritis. (9) As illustrated by the clinical case scenario, oligo-JIA usually has an indolent presentation. Features that are atypical for oligo-JIA include: joint erythema; acute onset of severe pain, resulting in an inability to bear weight; or hip involvement. It is common for children with oligo-JIA to modify their behavior in order to accommodate their arthritis, thus avoiding stressful positions that aggravate their affected joints. This ultimately results in disuse atrophy or joint contractures. A classic example is of the right-handed oligo-JIA patient who switches to use his or her left hand after developing right-wrist arthritis.

A positive anti-nuclear antibody (ANA) may be present in up to 85% of patients with oligo-JIA and uveitis. (10) Although patients with oligo-JIA may have a mild chronic anemia, inflammatory markers, such as erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) tests, are commonly normal in the setting of active arthritis or uveitis. The clinician should not be falsely reassured that the patient does not have active disease in the setting of normal labs.

Up to 50% of patients, who in the first 6 months present with oligoarticular arthritis, may later develop polyarthritis, involving five or more joints; these patients are reclassified as extended-oligoarticular JIA. (11) This subset of oligo-JIA is associated with poorer outcome and a lower likelihood of adult remission. Predictors of patients evolving into extended-oligoarticular JIA include: ankle, wrist, or hand arthritis; symmetric arthritis; arthritis in two to four joints; and the presence of an elevated ANA titer or ESR. (12) Uveitis is common in Oligo-JIA, and much like the arthritis, the chronic anterior uveitis of JIA is often asymptomatic, as children rarely report complaints, such as redness, pain, or changes in vision. The uveitis may also not correlate with the activity of the arthritis. Patients at highest risk for uveitis include ANA positive oligo-JIA patients, 20% to 30% developing eye disease. Other factors associated with increased risk include: female gender, under 6 years of age at diagnosis, and fewer than 4 years of disease duration. (13) Patients at high risk require frequent screening, with slit lamp examinations every 3 to 4 months. Most cases of anterior uveitis in JIA respond to topical steroids, yet some patients may be refractory to topical therapy, or develop iatrogenic complications from topical steroids. Glaucoma and cataracts are seen in approximately 4% to 15% and 10% to 23% of patients, respectively. (13,14)

Without appropriately aggressive treatment and close ophthalmologic follow-up, uveitis may result in further complications, such as synechiae (23%), band keratopathy (14%), macular edema (5%), and blindness (5% to 10%). (13) Therefore, systemic immunomodulatory therapy may be prescribed, including methotrexate, mycophenolate mofetil, and infliximab, as well as others. (15-17) Although anti-TNF therapy may be helpful in select patients with uveitis, etanercept does not appear to be effective and may even exacerbate uveitis. (18,19)

Polyarticular JIA

Polyarticular JIA (poly-JIA) accounts for 25% to 40% of JIA and is subdivided into RF positive and RF negative patients. RF-positive poly-JIA accounts for only 5% to 10% of JIA, implying that clinicians should be more selective when ordering laboratory tests, as there is a high false RF-positive rate in children. Unlike adult RA, anticyclic citrullinated peptide is not as helpful in JIA, and its presence is an inconsistent marker of disease. Seropositive poly-JIA patients have the identical clinical phenotype as adult RA: early-onset aggressive, erosive, and symmetric polyarthritis, with the potential for classic joint deformities, such as boutonniere and swan neck, and variable presence of rheumatoid nodules. In addition to common peripheral joint disease, these patients may also have involvement of the cervical spine and temporomandibular joint. While disease onset is commonly seen in children older than 8 years of age, it is more frequently encountered in adolescence, with a 90% female predominance. As this is essentially identical to adult RA, these children have a lifelong prognosis that is poor without appropriately aggressive treatment. Seronegative poly-JIA patients have a more variable prognosis and account for approximately 30% of JIA. Ninety percent of patients are female, with peak age of onset between 1 to 3 years, although it may occur at any time.

Although patients with polyarticular JIA may have constitutional features, such as fatigue, anorexia, weight loss, anemia, elevated inflammatory markers, morning stiffness, and low grade fever, they do not have the consistently high-spiking fever or rash, differentiating this from systemic-onset JIA. Unlike oligo-JIA, anterior uveitis is uncommon and patients, therefore, are recommended to have only yearly screening with slit lamp examinations.

All children with poly-JIA ultimately require disease-modifying anti-rheumatic drug (DMARD) therapy or a biologic agent such as anti-TNF-[alpha] therapy. As a bridging drug, corticosteroids are used sparingly, for their immediate antiinflammatory properties. As poly-JIA patients are at high risk for lifelong disease, their ability to be weaned off medication is questionable. Up to 60% of children may have arthritis flare after methotrexate is withdrawn. Fortunately, 90% of these patients will respond when methotrexate is restarted. (20)

Systemic-Onset JIA

Systemic-onset JIA (S-JIA) comprises 10% of JIA cases. Unlike other subsets of JIA, there is no gender disparity, and it may occur at any age. Uveitis is also very rare in this disease subset. S-JIA has essentially the same clinical phenotype as adult Still's disease and is characterized by daily high-spiking fevers for at least 2 weeks. The classic salmon-colored evanescent rash consists of discrete circumscribed macules that may be surrounded by a ring of pallor or develop a central clearing. This rash is found most commonly on the trunk, axilla, and inguinal areas, and may be exacerbated by fever, stress, or a hot bath, emphasizing the importance of a full skin exam when the patient is febrile. The arthritis of S-JIA is commonly polyarticular and usually presents within the first 3 months of onset. Since arthritis may not be present early, diagnosing S-JIA is more challenging, as the extra-articular features, such as serositis, fever, anemia, or hepatosplenomegaly, often predominate. Laboratory evaluation may reveal leukocytosis, thrombocytosis, anemia, hepatitis, and hyperferritinemia. ANA is rarely positive and rheumatoid factor is absent.

Although 60% to 85% of patients with S-JIA may experience a quiescent phase, up to 37% of patients develop chronic, erosive polyarthritis, requiring therapy with DMARDs or biologics, or both. (11) Predictors of poor prognosis in S-JIA include: age of onset under 6 years, disease duration for greater than 5 years, or persistent systemic features at 6 months of disease, including fever, the need for corticosteroids, and thrombocytosis. (21) Mortality is less than 0.3% for patients with S-JIA in North America, with the vast majority of patients dying from macrophage activation syndrome (MAS; a.k.a. reactive or secondary hemophagocytic lymphohistiocytosis syndrome), infection, or cardiac complications. Although an uncommon complication, the prevalence of amyloidosis is 1.4% to 9% in patients with S-JIA.

MAS is an uncommon but potentially life-threatening syndrome seen in S-JIA. There is debate among rheumatologists regarding whether MAS is a separate entity from S-JIA or rather an extreme variant within the spectrum of SJIA. MAS is characterized by impaired cytotoxicity of NK cells and CD8 positive T cells, resulting in an overwhelming cytokine storm with activated macrophages infiltrating organs, such as the bone marrow and liver. The diagnostic hallmark of MAS is the presence of well-differentiated, activated macrophages actively phagocytosing hematopoietic cells within the bone marrow. Inconsistent and debatable triggers of MAS include viral infections and the introduction of medications, including nonsteroidal anti-inflammatory drugs (NSAIDs), sulfasalazine, methotrexate, and etanercept. (22,23) Clinical features of MAS include: fever; pancytopenia; liver failure; coagulopathy with hemorrhage or thrombophilia, or both; encephalopathy; and seizures. A diagnosis of MAS carries an 8% to 22% risk of mortality. Laboratory features include markedly elevated ferritin, pancytopenia, prolonged PT and PTT, hypofibrinogenemia, elevated fibrin split products, and hypertriglyceridemia. A clinical pearl regarding MAS is the presence of a normal ESR in the setting of clinical deterioration, which likely signifies a worsening consumptive process with hypofibrinogenemia, thus resulting in a normal ESR. Patients often require intensive care unit (ICU) management for hemodynamic instability, hemorrhage, and seizure, with the majority of patients requiring high-dose pulse steroids and other immunosuppressive agents, such as cyclosporine A, etoposide, thalidomide, cyclophosphamide, or infliximab, based on anecdotal evidence and small case series. (24)

Pharmacotherapy for JIA

Nonsteroidal Antiinflammatory Drugs

NSAIDs are the mainstay therapy for the majority of patients, reducing the pain and inflammation of JIA. NSAIDs are commonly used as first-line agents and monotherapy in patients with oligoarticular JIA. Through inhibition of the cyclooxygenase (COX) pathway of arachidonate metabolism, NSAIDs prevent the production of the proinflammatory prostaglandins. More than six NSAIDs are approved for use in JIA by the Food and Drug Administration (FDA), with liquid formulations available of naproxen, ibuprofen, and meloxicam. Although side effects are encountered, NSAIDs are fairly well-tolerated in most children. A double-blind, double-dummy 12-month study of 225 JIA patients randomized to receive either naproxen or meloxicam demonstrated safe use in children, with abdominal pain the most common adverse event reported in 24% to 29% overall; this is higher than in other studies, including anecdotal reports. (25) In a similar 1-year open-label study of 286 JIA patients taking either rofecoxib or naproxen, abdominal pain and headache were reported in 6% to 13% and 12% to 15% of patients, respectively. (26) Nonselective NSAIDs are effective agents that are available in palatable liquid formulations and reasonable dosing regimens, which are important considerations when prescribing medication for children. In addition to this, the withdrawal of rofecoxib from the market, in 2004, due to concerns regarding increased risk of thromboembolic phenomenon are among the reasons that COX II inhibitors are not used as commonly in JIA. As there are few safety studies regarding the use of NSAIDs in JIA, there is a current 5-year registry that is seeking to collect further safety data of nonselective NSAIDs and celecoxib, a COX II inhibitor.

Intra-Articular Glucocorticoid Injections

Intra-articular (IA) glucocorticoid injections are often the treatment of choice in oligo-JIA, with persistent arthritis of one or two joints after a trial of NSAIDs. In addition to avoiding the adverse effects and parental challenges related to the administration of daily medicine to small children, IA steroids provide immediate, effective, local treatment. The clinician may elect to perform a joint injection earlier in the course, should there be significant leg-length discrepancy, muscle atrophy, or joint contracture. Sherry and colleagues demonstrated that children with oligo-JIA who received early administration of IA steroids within the first 2 months of disease onset had significantly less leg-length discrepancy than patients who had received primarily NSAIDs. (27) Intra-articular injections often result in a sustained response, with no recurrence of arthritis in up to 70% of patients at 1 year and 40% at 2 years followup. (28) A 1-year follow-up of gadolinium-enhanced MRI of joints injected with triamcinolone hexacetonide demonstrated markedly improved synovitis and no evidence of joint damage in all examined joints. (29) Should a patient have a recurrence of arthritis, the clinician may inject the same joint up to three-times in a year. Longer-acting triamcinolone hexacetonide (Kenalog[R] or Aristospan[R]) is the preferred preparation among rheumatologists.

Disease-Modifying Anti-Rheumatic Drugs in

JIA

Methotrexate (Rheumatrex[R])

Low-dose, weekly methotrexate has been used in the treatment of JIA for over 20 years. Methotrexate was demonstrated to be significantly more effective than placebo in a randomized, double-blind, placebo-controlled trial of 127 children with JIA. (30) In 1993, a meta-analysis of three prior clinical trials investigating oral gold, dpenicillamine, hydroxychloroquine, and methotrexate demonstrated 50% or greater improvement in 50% of the children given methotrexate at 10 mg/[m.sup.2]/week. (31) A recent study by Silverman and coworkers examining methotrexate and leflunomide reported an unprecedented ACR Pedi 70 response in 86% of poly-JIA patients taking methotrexate after 2 years of open-label medication. (32) Methotrexate is well-tolerated in children when given with folic acid, with many children safely tolerating oral or subcutaneous doses up to 30 mg. Ruperto and associates investigated the use of higher doses of parenteral methotrexate (intermediate dose: 15 mg/[m.sup.2]/week, and high dose: 30 mg/[m.sup.2]/week) in children with poly-JIA, who had not responded to 6 months of standard methotrexate doses of 8 to 12.5mg/[m.sup.2]/week. They concluded that those who had received the higher dose of methotrexate did not have a therapeutic response greater than those who received the intermediate dose of 15mg/[m.sup.2]. (33) Nevertheless, based on anecdotal evidence and personal experience, many pediatric rheumatologists may increase the dose of methotrexate to 1 mg/kg, up to 40 to 50 mg weekly. Although liver enzyme abnormalities are not uncommon, there have been no reported cases of severe irreversible liver fibrosis, and pulmonary toxicity, including nodulosis, is rare. (34) With its affordability and proven efficacy, safety and tolerability, methotrexate is the DMARD of choice against which all other DMARDs or biologics are judged.

Sulfasalazine (Azulfidine[R])

Sulfasalazine has been used extensively in adult RA for over 25 years. In Europe, prior anecdotal reports and open-labeled studies suggested efficacy of sulfasalazine in the treatment of JIA. (35,36) A 24-week randomized, double-blind, placebo-controlled, multicenter study of 69 patients with early-onset oligoarticular or polyarticular JIA was performed to determine the efficacy of sulfasalazine. (37) At week 24, patients receiving sulfasalazine demonstrated decreased joint pain and swelling and inflammatory markers in contrast to placebo, ultimately leading to its approval by the Food and Drug Administration (FDA). Of note, 29% of patients on sulfasalazine ultimately discontinued the medication due to adverse events, which were most commonly anorexia, abdominal pain, and rash. These side effects, as well as the proven efficacy of methotrexate and the discovery of biologics, may partly explain the less common use of this medication in the U.S.

Leflunomide (Arava[R])

In adults, leflunomide is a safe, well-tolerated and effective DMARD that may slow radiographic progression of RA. (38,39 ) Silverman and colleagues conducted a 16-week study of methotrexate versus leflunomide in 94 DMARDnai've poly-JIA patients. The investigation was a doubledummy, blinded design, followed by a 32-week blinded extension. (32) Response rates were unprecedented for both leflunomide and methotrexate, with patients achieving an ACR Pedi 50 of 73% and 86%, respectively, at 16 weeks. Furthermore, most responders were able to maintain this response in the 2-year open-label extension study, with 70% to 86% of patients receiving either medication achieving an ACR Pedi 50 or 70 at week 48. Most common adverse events included elevated liver enzymes, headache, abdominal pain, nausea and vomiting, diarrhea, alopecia, and viral infections. Serious adverse events, possibly related to treatment, included suspected salmonellosis, abnormal liver function tests, and parapsoriasis. Despite these impressive results, leflunomide did not receive FDA approval for JIA, due to concerns regarding inadequate plasma concentrations of its M1 active metabolite in children weighing under 40 kg. This may contribute to its lack of popularity among pediatric rheumatologists in the U.S.

Biologics in JIA

Anti-TNF[alpha] Therapy

Etanercept (EnbreP)

Etanercept is a soluble, dimeric, fusion protein consisting of the human p75 TNF receptor, fused to the Fc region of human IgG1. Etanercept is a well-tolerated, efficacious biologic for adults with RA. (40,41) In 1999, etanercept was the first biologic to receive FDA-approval for poly-JIA as a result of efficacy data from a randomized study in JIA. (6) This also proved to be the sentinel withdrawal study design in JIA, emulated by many subsequent JIA clinical trials. Sixty-nine patients with active poly-JIA, despite the use of NSAIDs and methotrexate, were enrolled in a multicenter, randomized, double-blind withdrawal study. After an initial 14-day methotrexate washout period, all patients received etanercept (0.4 mg/kg, max 25 mg) twice weekly for the first 3 months, as part of the open-label part of the trial. Stable doses of NSAIDs and low dose prednisone (less than or equal to 0.2 mg/kg, max 10 mg/day) were allowed. Seventy-four percent of patients were deemed responders, having achieved at least an ACR Pedi 30 after the first 3 months of etanercept monotherapy. These children were then randomized to etanercept withdrawal for months 4 through 7 until either disease flare occurred or 4 months elapsed. Patients randomized to continue etanercept for 4 months had a significantly longer median time to disease flare than the placebo group. Patients who flared restarted etanercept in the open-label extension.

Eight-year safety and efficacy data from a total of 318 patient-years, including 26 of the initial 69 patients who entered the eighth year of continuous treatment with etanercept, demonstrated that the long-term safety profile was maintained and exposure-adjusted rates of serious adverse events (SAEs) did not increase over time. The most common new SAE beyond 4 years consisted of arthritis flare, and there were no reported cases of malignancies, lupus, or demyelinating disorders. (42) Other follow-up studies also have supported improvement in growth and quality of life, as well as a sustained response with etanercept. (43,44) An Italian registry of 40 poly-JIA patients demonstrated radiographic improvement after 1 year of etanercept, in contradistinction to the previously held belief that these changes are irreversible. (45) Future prospective studies are necessary to validate this outcome. A German registry suggested improved efficacy in combination therapy with methotrexate, correlating with etanercept trials in adult RA. (46)

Adalimumab (Humira[R])

Adalimumab is a humanized IgG monoclonal anti-TNF[alpha] antibody, which is effective in reducing the pain, swelling, and joint destruction of adult RA. (47,48) Adalimumab was approved by the FDA, in 2008, for use in poly-JIA after a withdrawal study of 190 active poly-JIA patients, who had previously received NSAIDs with or without methotrexate. (49) All patients received open label 24 mg/[m.sup.2] (maximum 40 mg) of adalimumab subcutaneously every other week for 16 weeks. Patients who achieved an ACR Pedi 30 response were randomized in a double-blinded fashion to continue adalimumab or subcutaneous placebo for up to 32 weeks or until disease flare. After 100 weeks of the open-label extension, ACR Pedi 50 and 70 responses were achieved in 86% and 77% of patients, respectively. Furthermore, 40% of patients achieved an ACR Pedi 90 (equivalent of clinical remission) at 16 weeks, with a sustained response at up to 170 weeks of follow-up. Although 16% of patients demonstrated at least one positive test for an anti-adalimumab antibody, the presence of these antibodies did not lead to a greater incidence of adverse events or drug discontinuation. Counter intuitively, these antibodies developed in five of 85 (6%) patients receiving methotrexate, in contrast to 22 of 86 (26%) patients not receiving methotrexate. Unlike etanercept, the addition of methotrexate did not appear to provide any additional benefit in these patients. Adverse events were not common and usually were considered mild, such as infection and injection site reactions. Serious adverse events, perhaps related to adalimumab, were present in 14 patients, including viral infections, pharyngitis, and pneumonia.

Infliximab (Remicade[R])

Infliximab is an intravenous chimeric (mouse-human) IgG1 monoclonal antibody that binds both membrane-bound and soluble TNF[alpha]. Infliximab has been shown to be an effective agent in adult RA. (50,51) In 2007, a phase III multicenter, randomized, double-blind, and placebo-controlled study of 122 poly-JIA patients with persistent disease, despite methotrexate therapy, was conducted. (52) Patients were randomized to receive infliximab (3 or 6 mg/kg) or intravenous placebo infusions for 14 weeks, after which all patients received infliximab through week 44. Patients were randomized to either one of two groups. Patients in Group 1 received methotrexate plus infliximab through week 44. Patients in Group 2 received methotrexate plus placebo for 14 weeks, followed by methotrexate plus infliximab (6 mg/kg) through week 44. Although the difference in ACR Pedi 30 at week 14 between placebo and 3 mg/kg infliximab was not statistically significant (63.8% and 49.2%, respectively), after the 1 year open-label treatment with infliximab, ACR Pedi 50 and 70 responses were achieved in 70% and 52% of patients, respectively. Although generally well-tolerated, there were more serious adverse events, including infusion reactions, human anti-chimeric antibodies (HACAs) to infliximab and newly induced antinuclear antibodies in the 3 mg/kg group than the 6 mg/kg group, for unclear reasons. Decreased efficacy over time is perhaps attributed to the development of HACAs. As infliximab did not achieve a statistically significant difference in its primary end point of an ACR Pedi 30 at week 14 versus placebo, it did not receive FDA approval for JIA. Nevertheless, it is still commonly used off-label by rheumatologists, as infliximab is effective in JIA, based on the open-label study, as well as by anecdotal reports, case series, and personal experience.

Other Biologics in JIA

Anakinra (Kineret[R])

Although anti-TNF therapy is widely used in patients with JIA, it appears to be less effective in systemic-onset JIA. A survey of pediatric rheumatologists demonstrated that 54% of patients with S-JIA had a fair or poor response to etanercept. (53) IL-1 is another proinflammatory cytokine that has been implicated in the pathogenesis of JIA. (54,55) Anakinra is an IL-1 receptor antagonist that is FDA-approved for RA and has been investigated as a therapeutic option in JIA. An open-label trial of anakinra in nine S-JIA patients demonstrated dramatic resolution of fever in seven of nine patients, arthritis in six of eight patients, and laboratory parameters (ESR, leukocytosis, anemia, thrombocytosis) within the first week of therapy. (56) Although a recent trial of anakinra in 50 patients with JIA failed to demonstrate significant efficacy, subgroup analysis suggested higher response rates among the S-JIA subset, as is described in anecdotal reports, open-label trials, and case series. (57) Of course, it would be an over simplification to assume that IL-1 blockade would be the magic bullet for S-JIA, as it is an extraordinarily heterogeneous disease. A study by Gattorno and coworkers suggested two clinical S-JIA subsets. They defined IL-1 blockade "responders" (10/22, 45%) with a lower number of active joints and an increased absolute neutrophil count, in contrast to the "nonresponders" group. (58) A current phase II-III trial of anakinra in refractory S-JIA is underway, as well as trials using rilonacept, an IL-1 Trap, and ACZ885, a fully humanized monoclonal antibody binding IL-1 p.

Tocilizumab (Actemra[R])

Plasma levels of IL-6 may also be very elevated in patients with S-JIA and have been shown to correlate with arthritis, fever and thrombocytosis. (59) Transgenic mice over-expressing human IL-6 demonstrate impaired growth, commonly found in patients with S-JIA, resulting from chronic inflammation. (60) The use of tocilizumab, a humanized, monoclonal antibody against the IL-6 receptor, has demonstrated efficacy in open-label trials of S-JIA. (61) In 2008, Yokota and associates published the results of their phase III trial of 56 S-JIA patients with persistent disease, despite DMARD or biologic therapy, or both. (62) Eighty-eight percent (49/56) of patients had persistent fever, with a mean ESR of 44.5 mm/hr at baseline. After an appropriate DMARD-biologic washout period, tocilizumab infusion (8 mg/kg) was administered as monotherapy every 2 weeks for three doses to all patients during the 6-week open-label, lead-in phase. Subsequently, randomization to placebo occurred in the group of patients who achieved an ACR Pedi 30 response for the following 12 weeks, or until disease flare.

Patients who responded to tocilizumab were allowed to enroll in the open-label extension phase for at least 48 weeks. At week 6, ACR Pedi 50 and 70 responses were achieved in 86% and 68% of patients, respectively, including improvement in fever, thrombocytosis, and ESR. At the end of the open-label extension period, 90% of patients achieved an ACR Pedi 70 response by week 48, and corticosteroids were reduced by at least 50% in the majority of patients. Subanalysis regarding patients previously taking anti-TNF therapy were not presented. Adverse events included infusions reactions, gastrointestinal hemorrhage, bronchitis, and gastroenteritis. Three patients developed anti-tocilizumab IgE antibodies. An ongoing international phase III trial seeks to determine the ideal dosing regimen and continues to evaluate the efficacy of tocilizumab.

Abatacept (Orencia[R])

As with adults who have RA, a significant fraction of JIA patients may not respond to anti-TNF therapy, commonly after methotrexate failure as well. Rather than targeting cytokines, one may target the co-stimulatory signaling between antigen presenting cells and T cells that is essential for T-cell activation and proliferation. Abatacept is an intravenous, soluble, fully human fusion protein, consisting of the extracellular domain of CTLA-4, linked to a modified Fc portion of human IgG. Abatacept competitively binds to CD80 or CD86 on antigen presenting cells, which, therefore, cannot bind to CD28 on T cells, inhibiting successful T-cell activation. Abatacept has been successfully used in adult RA. (63,64) A phase III multicenter, double-blind and randomized controlled withdrawal study was conducted with abatacept in 190 patients with active poly-JIA, despite at least one DMARD. (65) All children initially received intravenous abatacept (10 mg/kg) during the 4-month open-label period, in addition to their prior stable dose of methotrexate, if applicable. Patients who achieved an ACR Pedi 30 were randomized to abatacept or placebo for the following 6 months or until disease flare. Patients on other DMARDs or biologics required a washout period of at least 4 weeks prior to abatacept.

Twenty-five percent (47/190) of patients did not respond to abatacept after the initial 4-month open-label period and were excluded from further randomization to placebo. Patients on abatacept had fewer flares of arthritis than placebo, 53% and 20%, respectively. At 4 months, ACR Pedi 50 and 70 were achieved in 50% and 28% of patients. Almost one-third of patients had previously discontinued anti-TNF therapy, and 25% of these patients were able to achieve an ACR Pedi 50 at 4 months, suggesting its efficacy in patients deemed "TNF failures." Adverse events were seen in 70% of abatacept patients and 55% of placebo, most commonly headache, nausea, diarrhea, cough, and upper respiratory infection. Serious adverse events were seen in six patients (3%), including arthritis flare, varicella, ovarian cyst, and acute lymphocytic leukemia, although retrospective review of the clinical data suggested that the leukemia preceded treatment with abatacept.

General Principles Regarding the Use of DMARDs and Biologics in JIA

Methotrexate is an effective DMARD in the majority of patients with JIA. It is important to be aware that many of the studies demonstrating efficacy of other DMARDs or biologics may pertain to the minority of JIA patients who are refractory to methotrexate. In addition to its efficacy, long-term safety data is available for methotrexate, as opposed to many of the newer biologics, which have only been used in JIA for the past 12 years. Although the newer biologics are very effective in the select patient, the clinician must also be aware of the cost of the medications, which can easily reach $15,000 a year. Among the various concerns of pediatric rheumatologists is the association of malignancy with immunosuppressive and disease modifying agents, an association described in the adult literature. In June 2008, the FDA released an early communication regarding 30 cases of cancer in children receiving anti-TNF therapy. Although biologics have revolutionized arthritis therapy, providing a target specific approach, there are other concerns, such as infection risk and vaccine responsiveness. In general, it is advisable to update all vaccinations prior to the initiation of therapy and avoid live vaccinations during DMARD and biologic therapy, or either alone.

Growth Disturbance

Although earlier diagnosis and initiation of more target-specific therapies have improved the outcome of children with JIA, growth impairment is not uncommon. Aberrant exposure to inflammatory cytokines, such as IL-6, and diminished growth factors, such as IGF-1, may result in early closure of growth plates, and permanent growth cessation. (60,66) As knee involvement is common, growth disturbance inducing a leg-length discrepancy can become clinically significant if the difference is greater than 0.5 cm. Micrognathia or irregular growth of the jaw with accompanying dysfunction may result from inappropriate endochondral ossification of the temporomandibular joint.

Children with systemic or polyarticular JIA may experience generalized growth impairment as a result of prolonged inflammation and, as well, the prolonged use of corticosteroids. Proinflammatory cytokines, including TNF-a, IL-1 and IL-6, are present in these subsets of JIA and can result in increased catabolic demands, anorexia, and cachexia. Despite the effects of uncontrolled inflammation and the adverse effects of medication, catch-up growth is still possible if the growth plates have not closed. If the growth plates have closed prematurely, the growth impairment is obviously permanent.

Outcomes

Much of the prior data regarding long-term outcome of JIA into adulthood are limited because of retrospective data collection, lack of or inadequate sub-typing of JIA onset, and an under-representation of the persistent oligoarthritis subtype, which tends to have a better long-term prognosis. Furthermore, all of the prior longer-term outcome data pertains to patients with JIA before the "age" of biologics. Despite these biases, JIA does not "burn out" as previously believed, with a significant fraction of adults having deformity, functional limitation, growth disturbance, or active arthritis as a consequence of their JIA. Zak and Pedersen retrospectively reviewed the charts of 65 patients with an average of 26.4 years of disease, discovering that 11% of patients had severe disability and 22% had undergone JIA-related surgery. (67) Packham and Hall investigated functional outcome in 246 JIA adults with an average disease duration of 28.3 years, including 50% oligoarticular-onset JIA, demonstrating shorter stature in contrast to the general population and micrognathia in 32.7%, especially in patients with S-JIA and RF negative poly-JIA. Twenty-three percent of these patients were still taking methotrexate. (14) In addition to functional impairment and active arthritis, adults with JIA may also have significant impairment of their quality of life, with a higher unemployment rate (24.6%), despite excellent educational achievement, compared to control populations. (68)

Summary

JIA is the most common rheumatic disease of childhood and may result in both short- and long-term disability, with persistent arthritis into adulthood. The prior JRA nomenclature is now included within the JIA classification, which also includes extended oligoarthritis, psoriatic arthritis, enthesitis-related arthritis, and undifferentiated arthritis. The majority of JIA consists of the oligo-JIA subtype, with 20% to 30% of ANA-positive patients developing asymptomatic anterior uveitis. Although this subtype of arthritis is often not very painful, significant deformity and growth disturbance may occur without appropriate therapy with NSAIDs and IA steroids, which are the treatments of choice. DMARD or biologic therapy may be required in extended oligo-JIA or uveitis. All poly-JIA patients will likely require aggressive DMARD or biologic therapy, or both, with RF-positive patients carrying a worse prognosis for lifelong disease. Systemic-onset JIA is an impressive inflammatory disease that may be complicated by MAS, requiring high-dose steroids and the addition of DMARD or biologic therapy, or both.

Currently, there are over 170 pediatric rheumatologists in the U.S. A large fraction of these physicians are active members of the various pediatric rheumatology study groups doing collaborative research, including CARRA, PRCSG, and PRINTO. If a pediatric rheumatologist is unavailable, many children with JIA may be cared for by adult rheumatologists, generalists, clinical immunologists, and other physicians. With continued collaborative research efforts, we hope to gain a better understanding of the biology and epidemiology of childhood arthritis, and, thereby, offer better therapies for our patients and improve the hope of a future cure. In the meantime, it is essential that the clinician focus on the elimination of disease activity, with the return to normal functioning, including school, and the prevention of disability in children with JIA.

Acknowledgment

The author would like to thank Herb Lazarus, M.D., for his thoughtful critique of this manuscript.

Disclosure Statement

The author has no financial or proprietary interest in the subject matter or materials discussed, including, but not limited to, employment, consultancies, stock ownership, honoraria, and paid expert testimony.

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Correspondence: Philip Kahn, M.D., L3 Medical, 160 East 32nd Street, New York, New York 10016; philip.kahn@nyumc.org.

Philip Kahn, M.D., is Assistant Professor of Pediatrics, New York University School of Medicine, and from the Division of Pediatric Rheumatology, Department of Pediatrics (Emergency Medicine Faculty), NYU Langone Medical Center, New York, New York.
A two-year-old female infant is seen for evaluation of
   her swollen right knee after a history of minor trauma.
   Upon further history, it is discovered that she has been
   limping frequently after very active days, for the past
   several months. On physical exam, the patient has a
   relatively painless, warm, right knee effusion with a
   10[degrees] flexion contraction. Arthritis of the right ankle is
   also discovered on closer physical examination.


A 15-year-old female is evaluated for fatigue, weight
   loss, morning stiffness, and diffuse musculoskeletal
   pain for the past 4 months. She has missed a few days
   of school and has quit the basketball team. The patient
   denies the presence of any fever or rash. On physical
   exam she has swollen, tender symmetric polyarthritis of
   multiple MCP (metacarpophalangeal) and PIP (proximal
   interphalangeal) joints, bilateral wrists, elbows,
   and ankles. She is rheumatoid factor (RF) positive and
   has multiple carpal bone erosions on hand radiographs.


A five-year-old male is admitted for further evaluation
   of his daily spiking fevers over the past 3 weeks and
   an intermittent rash. He is discovered to have pericarditis,
   hepatosplenomegaly, lymphadenopathy, elevated
   inflammatory markers, and pancytopenia, leading to
   further evaluation by infectious disease and oncology
   physicians. Polyarthritis is discovered on subsequent
   physical exam.


Table 1 Classification of Subtypes of Juvenile Idiopathic Arthritis

Systemic Onset
   Arthritis with or preceded by at least 2 weeks of
   daily fever, with at least 3 days of documented "quotidian" fever
   Plus one or more of the following:
      1. Evanescent, non-fixed erythematous rash
      2. Generalized lymph node enlargement
      3. Hepatomegaly and/or splenomegaly
   Exclusions 1 to 4
Oligoarthritis onset
   Persistent oligoarthritis
      Arthritis of 4 or fewer joints throughout disease course
   Exclusions 1 to 5
   Extended oligoarthritis
      Arthritis of 5 or more joints after initial 6 months of
       oligoarticular disease
   Exclusions 1 to 5
Polyarthritis onset
   Rheumatoid Factor negative
      Arthritis of 5 or more joints during initial 6 months of disease
      Rheumatoid factor negative
   Exclusions 1 to 5
      Rheumatoid Factor positive
        Arthritis of 5 or more joints during initial 6 months of
         disease
        Rheumatoid factor positive on two or more occasions, at least 3
         months apart
   Exclusions 1,2,3, 5
Psoriatic arthritis
   Arthritis and psoriasis
   or
   Arthritis and two of the following
      1. Dactylitis
      2. Nail pitting or onycholysis
      3. Psoriasis in a first-degree relative
Enthesitis related arthritis
   Arthritis and enthesitis
   or
   Arthritis OR enthesitis and two of the following
        1. Sacroiliac joint tenderness and/or inflammatory lumbosacral
           pain
        2. HLA B27 positive
        3. Arthritis in a male over 6 years of age
        4. Acute anterior uveitis
        5. History of ankylosing spondylitis, enthesitis-related
           arthritis, sacroiliitis with inflammatory bowel disease,
           reactive arthritis (Reiter's syndrome) or acute anterior
           uveitis in a first-degree relative
   Exclusions 1,4, 5
Undifferentiated arthritis
   Fulfills none of the above subsets
   or
   Fulfills more than one of the above subsets
Exclusion criteria for JIA
      1. Psoriasis or a history of psoriasis in a first-degree relative
      2. Arthritis in an HLA B27 positive male beginning after his 6th
         birthday
      3. History of ankylosing spondylitis, enthesitis-related
         arthritis, sacroiliitis with inflammatory bowel disease,
         reactive arthritis (Reiter's syndrome), or acute anterior
         uveitis in a first-degree relative
      4. IgM rheumatoid factor on 2 or more occasions at least 3 month
         apart
      5. Diagnosis of Systemic Juvenile Idiopathic Arthritis

Table 2 Criteria for Improvement in Juvenile Idiopathic
Arthritis

Core Set Criteria

1. Number of active joints (0-75)

2. Number of joints with loss of motion (0-67)

3. Physician's global assessment of disease activity by VAS (0-100)

4. Parent/Patient global assessment of overall well being by VAS
(0-100)

5. Functional assesment via Childhood Health Assessment
Questionnaire (0-3)

6. ESR

Patient must have at least a 30% improvement in 3/6 items and a
worsening of 30% in no more than one item to achieve an ACR Pedi 30
response.

ACR Pedi 50 and 70 response require 50% or 70% improvement in 3/6
criteria, and worsening of 30% in no more than one item

Additional Measures

1. Parent's global assessment of pain by VAS (0-100)

2. Parent's global assessment of arthritis by VAS (0-100)

3. Child's assessment of discomfort by facial affective scale (1-9)
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