Background The etiology of Juvenile Idiopathic Arthritis (JIA) remains unknown, despite a range of proposed mechanisms under investigation . However, previous research has revealed biological differences depending on the age of onset of JIA, independent of the classification based on the number of joints involved .
Objectives In this parent-led study, the age of onset of JIA by both disease subtype and sex of the child were explored, to identify whether there is a difference in age of onset of JIA between males and females.
Methods An online survey was shared via social media, targeted at parents of children and young people (CYP) with JIA. Questions probed the age of symptom-onset and diagnosis (by single year of age), JIA subtype and Rheumatoid Factor (RF) status.
Results Of the 409 CYP included, 296 had polyarticular (poly) or oligoarticular (oligo) JIA, including extended-oligo JIA (72% of all respondents). There were no differences between onset among these subtypes; therefore, they were grouped for further analysis, given comparable disease progression and genetic markers among these subtypes. There was no significant difference regarding age of symptom onset between RF-positive and RF-negative CYP. Amongst those with poly/oligo JIA, there was a clear peak of symptom-onset in the first few years of life, with over half experiencing symptoms before their third birthday, and 73% before the age of five years. Interestingly, the distribution of symptom-onset was significantly different in the poly/oligo JIA group between males and females (P=0.0093), with the onset of poly/oligo JIA appearing to occur earlier in females (Figure 1). Given that some CYP with older-onset JIA are sometimes reclassified as having enthesitis-related arthritis (ERA) when examined in adolescent services, the Mann-Whitney U Test was repeated with only those CYP with JIA onset before the age of seven years. In this case, there remained a significant difference in age of onset of poly/oligo JIA between males and females (P=0.0061).
Conclusion The age of symptom-onset among CYP with poly/oligo JIA differs between males and females, with females tending to exhibit symptoms earlier. This appears not to be attributable to misclassification of JIA subtype, and so this knowledge may assist future diagnoses of JIA. Further research is required to identify which temporal-associated factors may be critical in JIA onset and development.
References  Rigante, et al. The Etiology of Juvenile Idiopathic Arthritis. Clinic Rev Allerg Immunol 2015; 49:253.
 Barnes, et al. Biologic similarities based on age at onset in oligoarticular and polyarticular subtypes of juvenile idiopathic arthritis. Arth Rheum 2010; 62:3249-58.
Disclosure of Interests Richard Beesley: None declared, Simon Stones Consultant for: SS has provided consultancy services to Envision Pharma Group, though this is not related to the contents of this abstract., Speakers bureau: SS has undertaken speaking engagements for Actelion, eyeforpharma, Four Health, Janssen and Roche, though these are not related to the contents of this abstract.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.