Introduction to enthesitis-related arthritis
Enthesitis-related arthritis (sometimes referred to as juvenile spondyloarthritis) is the only form of juvenile idiopathic arthritis (JIA) that predominantly occurs in males, typically presenting in late childhood or adolescence. The classic sites for enthesitis (inflammation at the sites of tendon and ligament attachment to bone) are the Achilles tendon and plantar fascial attachment into the calcaneus, the poles of the patellae, and the greater trochanters. Arthritis occurs in peripheral and axial joints (sacroiliac joint and spine). Hip involvement early in the disease course or isolated severe disease of the midfoot is relatively common.
Similar to adults with axial spondyloarthritis, children and adolescents with enthesitis-related arthritis may experience symptomatic acute anterior uveitis; this is distinct from the asymptomatic anterior uveitis in young children with oligoarthritis. For information on acute anterior uveitis and its management, see JIA-associated uveitis.
In addition to uveitis, other extra-articular features can be associated with enthesitis-related arthritis (similarly to spondyloarthritis). Consider whether extra-articular symptoms in a patient with enthesitis-related arthritis are due to the disease itself or a comorbid disease (eg bowel symptoms may be due to comorbid inflammatory bowel disease)—see Overview of spondyloarthritis for information.
As in axial spondyloarthritis, human leucocyte antigen B27 (HLA-B27) positivity is typical in children with enthesitis-related arthritis. Axial spondyloarthritis will develop in a subset of children with enthesitis-related arthritis.