Objective. We recently hypothesized that in the International League of Associations for Rheumatology (ILAR) classification of juvenile idiopathic arthritis (JIA), the presumably homogeneous patient group characterized by early onset of disease, a female predilection, the presence of antinuclear antibodies (ANA), asymmetric arthritis, and the risk for iridocyclitis is classified into different categories. We sought to investigate whether ANA-positive patients belonging to the ILAR categories of oligoarthritis and rheumatoid factor (RF)-negative polyarthritis share homogeneous features and to compare these features with those of ANA-negative patients with JIA in the same categories. Methods. We identified patients who were followed up during a 15-year period. All patients had JIA according to the ILAR criteria, with oligoarticular or polyarticular onset. ANA positivity was defined as 2 or more positive results at a titer of ≥1:160. Demographic and clinical features, including the number of joints involved over time and measures of JIA severity at the last followup visit, were recorded retrospectively. Results. A total of 256 patients were included: 190 were ANA positive (109 had persistent oligoarthritis, 48 had extended oligoarthritis, and 33 had RF-negative polyarthritis), and 66 were ANA negative (35 had RF-negative polyarthritis, and 31 had oligoarthritis). All patients who were positive for ANA were similar in terms of age at disease presentation, female-to-male ratio, and frequency of symmetric arthritis and iridocyclitis. Compared with ANA-positive patients with polyarticular disease, ANA-negative patients with polyarticular arthritis were older at disease presentation and had a lower frequency of iridocyclitis, a higher frequency of symmetric arthritis, a greater cumulative number of joints affected over time, and a different pattern of joint disease, with a greater frequency of shoulder and hip involvement. The strong relationship between the presence of ANA and younger age at disease presentation, asymmetric arthritis, and development of iridocyclitis was confirmed by multivariate regression analysis. Conclusion. Our results support the hypothesis that patients with similar characteristics are currently classified into different JIA categories. The value of ANA positivity as a possible modifier of the current classification system deserves consideration.
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