TOPLINE: 

Infants with early-onset juvenile idiopathic arthritis (JIA) showed distinct characteristics; patients with disease onset at or before 12 months were more likely to have systemic/rheumatoid factor-negative polyarticular JIA and involvement of small joints, whereas those with onset at 13-24 months tended to have oligoarticular JIA with higher antinuclear antibody positivity.

METHODOLOGY:

• Researchers conducted a multicenter retrospective cohort study to determine the clinical, laboratory, and outcome features of patients in whom onset of JIA was at or before 2 years of age, using data from records of 14 pediatric rheumatology centers.
• They included 199 patients (mean age at symptom onset, 16.9 months; 75.9% girls) who were followed up for at least 6 months. Infants with symptom onset at or before 12 months comprised the early-onset group (n = 40).
• Demographic, clinical, laboratory, and treatment information was collected, and the Juvenile Arthritis Disease Activity Score and remission status were assessed using the 2011 American College of Rheumatology/Wallace criteria.
• Clinical characteristics were compared between patients with early onset and those with onset after 12 months.

TAKEAWAY:

• Patients in whom JIA began at or before 12 months were significantly more likely to have rheumatoid factor-negative polyarticular JIA (25% vs 8.2%; P = .002) and systemic JIA (25% vs 10.7%; P = .002), whereas those with onset after 12 months predominantly had persistent oligoarticular JIA (65.4% vs 37.5%; P = .002).
• Antinuclear antibody positivity was higher in patients with disease onset after 12 months (P = .011), but uveitis was more common in those with early onset (P = .034).
• Involvements of the wrist (40% vs 16.4%; P = .001), hand proximal interphalangeal joints (32.5% vs 17.6%; P = .037), and foot proximal interphalangeal joints (10% vs 1.9%; P = .031) were more frequent in those with early-onset disease than in those with onset after 12 months.
• Remission was achieved in 72.5% of patients with early onset after a median follow-up duration of 54 months, compared with 79.2% of those with later onset over a median follow-up duration of 38 months.

IN PRACTICE:

"This study demonstrated that patients with symptom onset during the infantile period may exhibit differences in terms of JIA category, affected joints, and development of uveitis. Therefore, we suggest that the question of 'how early is early' should be asked when referring to the age of disease onset in JIA," the authors wrote.

SOURCE:

This study was led by Kubra Ozturk, MD, Istanbul Medeniyet University in Istanbul, Türkiye. It was published online on August 14, 2025, in Rheumatology.

LIMITATIONS:

The study was retrospective in nature and had a relatively small sample size of infants with disease onset before 12 months.

DISCLOSURES:

No specific grants were received for this study. The authors declared having no conflicts of interest. 

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.