Outcome in Juvenile Idiopathic Arthritis

A Population-Based Study From Sweden

Elisabet Berthold; Bengt Månsson; Robin Kahn

Disclosures

Arthritis Res Ther. 2019;21(218) 

In This Article

Background

Juvenile idiopathic arthritis (JIA) is the most common rheumatic disease in children, with an unpredictable clinical course and the impending risk of impaired joint function. JIA is an umbrella term encompassing a heterogeneous group of inflammatory arthritides of unknown etiology, all defined by the presence of at least one inflamed joint persisting ≥ 6 weeks, beginning before 16 years of age and that cannot be explained by other causes such as infection or trauma.[1] Historically, different names have been used for the disease, with juvenile rheumatic arthritis (JRA) with 6 weeks duration of arthritis being the American definition[2] and juvenile chronic arthritis (JCA) with arthritis enduring for at least 3 months being the European definition.[3] The present international consensus of JIA is based on the criteria defined by the International League of Associations for Rheumatism (ILAR) in 2001. According to these criteria, JIA is further divided into seven subcategories based on clinical features: enthesitis-related arthritis (ERA), oligoarticular JIA (persistent and extended), polyarticular rheumatoid factor-negative (RF−) JIA, polyarticular RF-positive (RF+) JIA, juvenile psoriatic arthritis (JPsA), systemic JIA (sJIA), and undifferentiated JIA (uJIA).[4]

The reports on incidence rates of JIA differ depending on the study design and geographic region. The worldwide incidence rate among Caucasians was in 2014 presented to be 8.3/100,000/year and the prevalence as 32.6/100,000/year.[5] These pooled rates were however based on studies using the three different disease classifications (ILAR, ACR, and EULAR). The incidence rates of juvenile arthritis differ between 15.0/100,000/year in the Nordic countries (ILAR),[6] 10.3/100,000 in Minnesota (USA) (ILAR and ACR),[7] 8.5/100,000 in Manitoba (Canada) (ILAR),[8] 6.9/100,000 in Catalonia (Spain) (ILAR),[9] and 3.1/100,000 in Alsace (France) (ILAR).[10]

The long-term outcome of JIA has improved in the last three decades.[11] There are different criteria developed to study and define disease outcome. In 2004, Wallace et al. defined a set of criteria for evaluation of clinical outcome in JIA. Inactive disease was defined as a state of no joints with active arthritis, no uveitis, no systemic symptoms, normal erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP), and a physician's global assessment of disease activity indicating no disease activity.[12] Using this definition, 47.5 ± 22.6% of the children achieved inactive disease after a median time of 6.5 ± 1.5 years, according to the data compiled in a review article on JIA outcome. Inactive disease and remission were achieved most often in the persistent oligoarticular subgroup, in contrast to the extended oligoarticular and RF+ subgroups, where the prognosis for achieving remission was least favorable.[13] In the most recently published outcome study, 45.6% of the children had active disease at 18 years of follow-up.[14] However, validated outcome criteria are difficult to use in a retrospective study due to the need for patient-reported measures.

Data on the rates of joint corrective surgery is sparse, but in a study on prevalent cases of JIA in Minnesota (USA) 1994–2013, 7% of the children with JIA had to undergo joint surgery during childhood with the same number needing it in adulthood.[15] In an older observational study on adult patients with JIA followed over a median time of 19 years, 28.5% had undergone joint surgery, with a majority needing joint replacement. Survival analysis showed that joint surgery was needed in more than 75% of the patients at 45 years disease duration.[16]

Uveitis is the most common extra-articular manifestation of JIA, and the reported prevalence range from 11.6 to 30%.[17] In the prospective Nordic cohort study with JIA patients collected 1997–2000, uveitis occurred in 89 (20.5%) children, 80 chronic and 9 acute cases, during a median follow-up of 98 months. There were no uveitis cases among patients with systemic or RF+ JIA.[18] In Sweden, children with JIA have regular ophthalmologic controls ≥ 1 time per year until the age of 14, to discover chronic uveitis.

The aim of this study was to investigate the epidemiology and outcome of JIA and to characterize the demographics of the patients with JIA, using a well-defined population-based cohort of children with a validated diagnosis of JIA collected over 9 years.

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