JIA: Small knee, big pain

7. November 2011
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The typical rheumatism sufferer is thought of as a geriatric patient – but idiopathic arthritis also affects children. Diagnosis and therapy in some cases differ significantly from that of "grown-up" patients.

In cases where joint inflammation in children lasts longer than six weeks, after exclusion of other causes rheumatism should always enter the realm of possibilities. If the ailment continues for more than three months, the diagnosis of juvenile idiopathic arthritis (JIA) is almost certain. As a first examination, a differential blood count, including erythrocyte sedimentation rate, is a sensible one. Liver function parameters, CRP, LDH, BUN, creatinine, and uric acid determination complete the set of results.The issue of whether the child is suffering from an infectious disease or has recently been bitten by a tick is also important. Lyme disease can also cause persistent arthritis. The type and number of affected joints as well guide the decision process in therapy.
Juvenile Idiopathic Arthritis (JIA) is a chronic disease with seven subgroups according to the International League Against Rheumatism (ILAR) classification:

• Systemic Arthritis
• Oligoarthritis
• RF negative polyarthritis
• RF positive polyarthritis
• psoriatic arthritis
• enthesitis related arthritis
• other non-differentiated arthritis

Inflammation without redness

Calor, dolor, tumor, rubor – these are the well-known signs of inflammation. In children, this is not always so. Pain is perceived differently, and redness of the affected joints is seen in children with chronic arthritis very rarely. In children under eight years, mostly one to four joints are affected. Large joints such as knee and ankle joints are usually affected asymmetrically. In more than half of the children antinuclear antibodies can be detected. If the children are older, the polyarthritis tends to be more symmetric, with five or more, usually smaller, affected joints.The determination of rheumatoid factor is rarely useful. This parameter is only positive for the mere five percent of all patients with juvenile idiopathic arthritis. Quite often, infections also give a false-positive outcome. A typical sign of juvenile idiopathic arthritis is the occurance of frequent bouts of fever.

Keep eyesight in mind

One in four children suffering from JIA contracts uveitis. If this inflammation is only discovered when a refractive error is detected, it leads in 80 percent of cases to almost complete blindness. In cases of suspected JIA, children, especially when under seven years, should be referred to an eye specialist for a slit-lamp examination every six weeks over the first two years. In general, children who first suffer from uveitis and then later arthritis have a worse prognosis. Particularly affected are children with ANA-positive oligoarthritis. Antinuclear antibodies (ANA) are directed against various components of the cell nucleus and may lead to disruption of nuclear and cellular functions. In August 2008 approval extension for adalimumab was secured for the treatment of active polyarticular juvenile idiopathic arthritis in combination with methotrexate, in justified cases as a monotherapy as well. The application is carried out every two weeks as a subcutaneous injection. Infliximab and adalimumab studies show good results in the treatment of ocular inflammation. No TNF-a inhibitor is currently approved for uveitis therapy.

Special form: psoriatic arthritis

One special form of JIA is juvenile psoriatic arthritis. The psoriasis often first occurs only after arthritis. Psoriatic nail developments (dappled nail, thickening) or dactylitis often occur as comorbidities. Regardless of what type of arthritis it is: treatment must be made as early as possible.

For analgesic and anti-inflammatory action, acidic analgesics such as ibuprofen, naproxen and diclofenac enter the picture. Inflamed tissues are made acidic by arachidonic acid and in such acidic tissue only an acidic analgesic can anneal to the area and have antiphlogistic effects. Non-acidic analgesics such as paracetamol and metamizol don’t have anti-inflammatory effects. In addition to pharmacological analgesia, the use of cool packs is very useful.

Methotrexate

In basic therapy, methotrexate (MTX) in low dosage and intra-articular glucocorticoids are used. The effect of methotrexate is often delayed. This three-to-four-week delay interval can be covered with low-dose cortisone. 80 percent of children respond well to methotrexate and they tolerate the substance better than adults. Changes in liver parameters and blood disorders occur in this age group as rarities. MTX usually strikes adults in the stomach and can lead to gastritis. Children under ten years almost never need a proton pump inhibitor. For those over ten years of age, in ten percent of cases gastrointestinal intolerance occurs. In an international study by Voell and colleagues, it was noted that the timing of withdrawal of methotrexate after achieving remission has no effect on the likelihood of relapse. “Our study thereby impressively refutes the previous assumption that a longer follow-up treatment with MTX has an influence on the risk of relapse,” says Prof. Voell. Six months seems to be enough. For the patient this means a significant gain in quality of life, because they can get off the drugs earlier than before.

Cytokines as the target of biologicals

If methotrexate is not tolerated or does not have an adequate effect, biologicals and cytokine antagonists can be employed. TNF-inhibitor etanercept has proven itself particularly effective. Abatacept is approved as the second signal-transduction inhibitor for those six years of age onward and TNF-antibody adalimumab for those of youth age and older. For children, IL1-receptor antagonist anakinra as well as IL6 antibodies although effective are not permitted. The interleukin-6 inhibitor tocilizumab is approved for the treatment of systemic juvenile idiopathic arthritis (SJIA) in children aged two years and over. In this particularly severe form, organ damage to heart, liver and spleen occur. Growth disorders are common with persistent inflammation and will be heightened by cortisone therapy with doses that are too high and given for too long. The estimated overall mortality rate is 2 to 4 percent. The approval is based partly on the results of international, randomised, double-blind TENDER Study. 112 children were additionally assigned to receive tocilizumab or placebo-based therapy.

Malignancy rather than rheumatism?

TNF inhibitors and other biologicals have expanded the treatment options for JIA significantly. The efficacy of etanercept and adalimumab has been demonstrated in randomised, controlled clinical trials. Long-term safety is nevertheless, especially in the treatment of children, of particular importance. Reports of leukemia and tumors in children and young people treated with etanercept, infliximab and adalimumab raise questions about an increased risk of malignancy. Lymphomas are, with 50 percent of cases reported to the regulatory authorities (American FDA), the most widely reported. As part of the choice process, a family history should be carried out with respect to malignancy or pre-treatment exposure to carcinogenic agents such as cyclophosphamide. This is what the Society for Pediatric and Adolescent Rheumatology (GKJR) calls for in a statement in response to the warning from the FDA.
The American College of Rheumatology has developed new guidelines for the treatment of juvenile idiopathic arthritis:

• Initiation of treatment with TNF-α inhibitors in children with arthritis in four or fewer joints and significant active arthritis despite treatment with methotrexate;

• Initiation of treatment with TNF-α inhibitors in children with arthritis in five or more joints and active arthritis after an appropriate assessment of methotrexate;

• Initiation of treatment with anakinra in children with systemic arthritis and active fever, whose treatment requires a second drug in addition to systemic glucocorticoids.

The treatment of rheumatic diseases in childhood should be carried out as an interdisciplinary process. In the best possible case, orthopaedic surgeons, rheumatologists, paediatricians and psychologists are involved. In Munich, Germany, rheumatologists have established an association in order to allow for earlier diagnosis and to improve the care of affected children: Rheumatic-Help for Children (Munich) supports children and adolescents with rheumatic diseases, provides school/training and consulting programs and promotes research in the field.

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