Enthesitis in an inception cohort of enthesitis-related arthritis

To describe an enthesitis-related arthritis (ERA) inception cohort and determine which entheses and joints are most commonly affected.

We reviewed a retrospective inception cohort study of children with ERA who were diagnosed and treated at The Children's Hospital of Philadelphia between November 2007 and December 2009.

During the study period, there were 32 newly diagnosed ERA patients. Fifty-nine percent were male, and the median age at the date of initial evaluation was 12.5 years (interquartile range [IQR] 10.2-14.3 years). The median number of tender entheses at presentation was 2 (IQR 0-5), and 21 subjects (66%) had at least 1 tender enthesis. The most prevalent tender entheses were the patellar ligament insertion at the inferior pole of the patella, the plantar fascial insertion at the calcaneus, the Achilles tendon insertion at the calcaneus, and the plantar fascial insertion at the metatarsal heads. Enthesitis was most often symmetric. The median number of active joints was 2 (IQR 0-4). The most commonly affected joints were the sacroiliacs, knees, and ankles. Sacroiliitis, which was defined clinically, was most often symmetric, while peripheral arthritis was most frequently asymmetric. The odds of having active enthesitis at 6 months increased significantly with each additional tender enthesis at the initial evaluation.

Among pediatric patients with ERA, lower extremity enthesitis is prevalent at the time of diagnosis and is likely to persist 6 months later. Future studies should address standardization of the enthesitis examination, the pattern of enthesitis over time, enthesitis response to therapy, and the impact of enthesitis on quality of life.