P011 Radiological pattern in juvenile onset Spondylarthritis differ from the adult onset spondylarthritis

Abstract Background Spondylarthritis (SpA) is a chronic inflammatory disease of the axial spine that may be affect the peripheral joints. SpA occurs predominantly in adulthood: Adult onset Ankylosing Spondylitis (AoAS). However, it can occur earlier in childhood (≤16 years old), also termed as juvenile onset Ankylosing Spondylitis (JoAS). In the second group, delay in diagnosis may lead to further structural damage. The aim of our study was to compare the differences in radiographic features between JoAS and AoAS. Methods We conducted a retrospective study in our department of rheumatology of Kassab Institute of orthopedics, including patients diagnosed with SpA according to the ASAS criteria (≥17 years at symptom onset) or to the ILAR criteria (≤16 years at symptom onset). Were not included AS patients whose disease onset was ≥ 45 years. Sociodemographic as well as disease characteristics were recorded. The lateral cervical and lumbar spine radiographs were used to assess structural damage by the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) and The Bath Ankylosing Radiologic Index (BASRI). The total score of mSASSS and BASRI vary between 0–72 and 0–16 respectively with higher scores indicating evolved structural damage. Radiographic features were then compared between AoAS and JoAS. The level of significance was fixed for a P < 0.05. Results Of 140 AS patients, 40 had JoAS and 100 had AoAS. The average age at disease onset was 12.4 ± 3 [8–16] and 25.4 ± 10.1 [17–42] respectively (P < 0.001). The disease duration was 10.6 years [1–44]. The average current age was 25.3 ± 10.2 [9–59] and 32.5 ± 7.5 [18–46] (P < 0.001). The JoAS group showed a more frequent onset with peripheral joint involvement than the AoAS group (80% vs 50%,P = 0.001). Similarly, hip involvement was more frequent among JoAS patients (57.7% vs 25%, P = 0.000). There was no significant differences between the two groups regarding the mean mSASSS score, the total BASRI score and the BASRI score for the sacroiliac joints (P = 0.9, P = 0.49, P = 0.06 respectively). Similarly, there was no differences in the mean spine BASRI score between the two groups, although there was a trend of higher scores among AoAS patients (3.2 vs 3.9, P = 0.15 respectively). On the contrary, JoAS patients had a significantly higher BASRI score for the hip than AoAS patients (2.4 vs 1.3, P = 0.000). Conclusion Our study showed that JoAS patients are more likely to suffer from early hip damage than AoAS patients. The spine BASRI was similar between the two groups despite the shorter disease duration in the juvenile group. This highlights the need for screening for hip involvement and for a closer monitoring in this subset of children.