Background/Purpose: There are no large radiographic follow up studies assessing progression in juvenile-onset Ankylosing Spondylitis (JoAS) as compared to adult-onset Ankylosing Spondylitis (AoAS). The purpose of this study is to examine the clinical and imaging aspects of JoAS in a large spondylitis clinic.

Methods: The spondylitis clinic has a database of around 1300 patients with confirmed ankylosing spondylitis (AS) as defined by the modified New York criteria. AS patients with symptom onset of back pain at 16 years of age or under were classified as JoAS. They were then matched by gender and duration of back pain to patients with symptom onset of back pain over 16 years old, defined as AoAS, in a 1:2 ratio. Clinical and radiographic data were then extracted. The analysis utilized linear or logistic regression analysis to correct for disease duration, gender, prior anti-TNF exposure, ESR, and HLA-B27 status as appropriate.

Results: 158 JoAS patients were identified and matched to 316 AoAS patients. There was a total of 365 males and 106 females. Baseline mean BASDAI was 4.36 for JoAS and 5.00 for AoAS and was not significantly different when adjusted for prior anti-TNF use. However, patient global disease activity was 4.38 for JoAS and 5.16 for AoAS, which was significantly different (p=0.032) after adjusting for prior anti-TNF use. Current and previous history of smoking exposure, iritis, and psoriasis did not differ between JoAS and AoAS. There was more associated Crohn’s disease in JoAS (13%) versus AoAS (4%), p=0.001. There was no difference in B27 status between the two groups. Baseline mSASSS was lower in JoAS (3.9%) vs AoAS (11.6%), and was statistically different when corrected for prior anti-TNF, duration of back pain, gender, baseline ESR, and B27 status (p<0.001). When followed over time, progression of 1 mSASSS unit or more yearly was lower in the JoAS (11%) vs AoAS (24%), and was still significant when corrected for gender, prior anti-TNF use, ESR, and HLA-B27 status, p=0.018. Progression of 4 mSASSS units or more over any time period was lower in the JoAS (14%) vs AoAS (35%), and was still significant when corrected for the covariates above, p=0.001. More JoAS (65%) were on biologics compared to AoAS (47%), p<0.001. Of the patients on biologics, more JoAS (52%) had switched biologics compared to AoAS (33%), p=0.006.

Conclusion: The rate of axial radiographic progression over time was lower in the JoAS cohort when corrected for covariates. JoAS patients were also on more biologics and switched biologics more regularly compared to AoAS patients.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/juvenile-onset-ankylosing-spondylitis-has-a-lower-rate-of-radiographic-progression-than-adult-onset-ankylosing-spondylitis/