Patients with very early-onset systemic juvenile idiopathic arthritis exhibit more inflammatory features and a worse outcome.

OBJECTIVE: Systemic juvenile idiopathic arthritis (SJIA) frequently leads to disability and damage. Predictive factors for a poor outcome include persistent systemic features and younger age at onset. We describe and analyze disease features in patients with early-onset (EO) SJIA (disease onset before age 18 mo) and compare them to patients with later-onset (LO) disease.
METHODS: Clinical features at onset, activity measures (occurrence of macrophage activation syndrome, remission), and outcome measures for disability [Childhood Health Assessment Questionnaire (CHAQ) ≥ 0.5] and damage [radiographic joint destruction, Juvenile Arthritis Damage Index (JADI) score, growth retardation] observed during followup were analyzed retrospectively in patients with SJIA followed for ≥ 3 years since disease onset.
RESULTS: In total 132 patients were included. SJIA started at age ≤ 18 months in 19 (14%) patients and at a later age in 113 (86%) children. At onset, serositis (p < 0.01) and hepatomegaly (p < 0.05) were more frequent in EO patients, who also exhibited lower hemoglobin levels (p < 0.03) and higher platelet counts (p < 0.03) than patients with LO. Macrophage activation syndrome occurred in 20 patients (11 EO and 9 LO; p < 0.0001). Remission was achieved by 49 patients (37%; 4 EO and 45 LO). At last visit, destructive hip disease (p < 0.04), growth retardation (p < 0.01), radiographic damage (p < 0.02), and disability (p < 0.04) were more frequent in patients with EO disease, who had higher JADI scores (p < 0.003).
CONCLUSION: Patients with EO exhibited a more aggressive and destructive disease course than patients with LO SJIA.