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Characteristics and Course of Enthesitis in a Juvenile Idiopathic Arthritis Inception Cohort
Dax G Rumsey1, Jaime Guzman2, Alan M Rosenberg3
1University of Alberta, Edmonton, Alberta, Canada.
Insights
Enthesitis affects 16% of children with juvenile idiopathic arthritis (JIA), often presenting with polyarthritis rather than enthesitis-related arthritis (ERA). The course of enthesitis in JIA patients mirrors active joint inflammation over time.
Area of Science:
- Pediatric Rheumatology
- Inflammatory Arthritis
- Musculoskeletal Diseases
Background:
- Juvenile idiopathic arthritis (JIA) is a heterogeneous autoimmune disease.
- Enthesitis, inflammation at tendon or ligament insertions, is a key feature in some JIA subtypes.
- Understanding enthesitis prevalence and course is crucial for JIA management.
Purpose of the Study:
- To determine the prevalence of enthesitis in a Canadian JIA inception cohort.
- To describe characteristics associated with enthesitis in JIA.
- To analyze the longitudinal course of enthesitis in relation to joint disease activity.
Main Methods:
- A prospective inception cohort of 1,406 Canadian children newly diagnosed with JIA (2005-2010) was followed for up to 5 years.
- Entheseal tenderness was assessed at 33 sites at multiple time points (0-60 months).
- Enthesitis was defined as tenderness at >1 site or on >1 occasion; statistical analyses included descriptive statistics and linear mixed models.
Main Results:
- 16% (219/1406) of JIA patients exhibited enthesitis.
- Children with enthesitis were older, more frequently male, and had higher rates of polyarthritis and sacroiliac involvement.
- Most enthesitis cases (64%) were not classified as enthesitis-related arthritis (ERA); common sites included calcaneal plantar fascia and Achilles tendon insertions.
Conclusions:
- Enthesitis is present in 16% of JIA patients, with a significant proportion not fitting the ERA classification.
- Enthesitis in JIA is often associated with polyarticular disease.
- The clinical course of enthesitis parallels that of active joint disease in JIA.
Objective:
To describe the prevalence, associated characteristics, and course of enthesitis in a juvenile idiopathic arthritis (JIA) inception cohort.
Methods:
Canadian children newly diagnosed with JIA between 2005 and 2010 were categorized using International League of Associations for Rheumatology criteria at the 6-month visit and followed in the Research in Arthritis in Canadian Children Emphasizing Outcomes (ReACCh-Out) cohort for up to 5 years. The presence of entheseal tenderness on examination at 33 sites shown on a homunculus was recorded at 0, 6, 12, 18, 24, 36, 48, and 60 months after enrollment. Enthesitis was defined as entheseal tenderness at more than 1 site or on more than 1 occasion. Analyses consisted of descriptive statistics and linear mixed models for longitudinal data.
Results:
Of 1,406 patients, 219 (16%) had enthesitis and, of those with enthesitis, 141 (64%) were classified as having enthesitis-related arthritis (ERA). Children with enthesitis were more often older (10.7 versus 7.5 years), male (57% versus 31%), and with polyarthritis (57% versus 41%) and sacroiliac involvement (30% versus 4%). Entheseal tenderness was most frequent at the calcaneal plantar fascial insertion (39%), Achilles tendon insertion (31%), and tibial tuberosity (30%). The mean number of tender entheseal sites decreased in parallel with active joint counts. There was no difference in active joint counts over time in children with or without enthesitis (P = 0.73).
Conclusion:
Enthesitis was observed in 16% of patients with JIA, but only two thirds were categorized as having ERA. Contrary to expectations, most children with enthesitis had polyarticular involvement. The course of enthesitis paralleled the course of active joint counts.