Enthesitis related arthritis (ERA) is a sub-type of juvenile idiopathic arthritis (JIA) that typically affects young males with onset most commonly seen in late childhood or early adolescents. It is said to be a distinct disease entity from ankylosing spondylitis (AS), with peripheral joint involvement and entheseal disease common at presentation and axial involvement a late feature. However, little is known about the natural history of ERA, with no long-term observational studies. The rationale for current treatment is largely based on extrapolation of evidence from other conditions, such as adult AS or other forms of JIA.
With greater use of MRI in children and adolescents, it is emerging that spinal disease in fact occurs earlier than previously thought in a significant proportion of patients with ERA. This talk will discuss the evidence from our cohort of around 70 patients along with some evidence from other published patient cohorts to suggest that there may in fact be 2 distinct clinical phenotypes of ERA: a predominantly axial from of ERA, whereby sacroiliitis as confirmed by MRI scanning is found early in the course of the disease which is strongly associated with hip arthritis and HLAB27 positivity and a second group who lack sacroiliitis but have a greater frequency of ankle arthritis and enthesitis and lower rates of HLAB27 positivity. Both groups fulfill the revised ILAR classification criteria for ERA.
Further characterization of these clinical phenotypes through long-term observational studies coupled with basic science research investigating the aetiopathogenic mechanisms driving these two clinical patterns of disease may lead to a better understanding of ERA and how best to treat it.
Disclosure of Interest None Declared