Background/Purpose: Musculoskeletal (MSK) manifestations, including arthritis and arthralgia, are among the most common extraintestinal manifestations (EIMs) of inflammatory bowel disease (IBD), reported in 20-30% of adult patients. While patterns of MSK EIMs have been well-characterized in the adult population, there remains a paucity of data in pediatrics. The purpose of this study was to determine the frequency of MSK EIMs in a contemporary cohort of Canadian pIBD patients and describe the phenotype of MSK EIMs in this population.

Methods: This was a prospective longitudinal cohort study using data from the inception cohort of CIDsCaNN (Canadian Children IBD Network). This is a national network involving 12 academic pediatric centers in Canada. The inception cohort is comprised of patients aged 2 to 17 enrolled at diagnosis and followed prospectively. The study included data from creation of the inception cohort (01-04-2014) to the end of the previous calendar year (31-12-2021). Frequency of MSK EIMs was calculated for the entire inception cohort, as well as for subgroups based on age ( < 5, 5 to 12, and 12 to 17), sex, and IBD type. For patients with MSK EIMs, phenotype was described by analyzing case report forms for specific EIM features as reported by treating physician. Variables were compared with Pearson Chi-square or Fisher’s exact test, where cell counts were < 5. Statistical significance was defined as two-tailed p-value < 0.05. For patients without MSK EIM at time of IBD diagnosis, a Cox regression survival analysis was used to examine differences in age, sex, and ethnicity in terms of time to MSK EIM development, with right censoring for patients who never reported MSK EIMs over the course of follow up.

Results: A total of 1330 pIBD patients were included. 81 patients (6.1%) were reported to have MSK EIMs at IBD diagnosis or any point during follow up. There was no significant difference in overall MSK EIM frequency between sex or age groups. MSK EIMs were present in 63 CD (7.6%), 10 UC (2.6%), and 8 IBD-U (6.4%) patients. Patients with CD were more likely to have MSK EIMs than those with UC or IBD-U (7.6% vs 3.6%, p=0.002). 47 patients (58.0%) had MSK EIMs at or prior to IBD diagnosis while 34 patients developed MSK EIMs >4 weeks after IBD diagnosis. There was no difference in time to MSK EIM development by age or ethnicity. Females were more likely to develop MSK EIMs after IBD diagnosis than males, with odds of MSK EIM development increasing by factor of 4.68 for each year after IBD diagnosis (p=0.047). Of MSK EIM patients, 59 (74.7%) were evaluated by a rheumatologist. Peripheral MSK disease (arthritis, enthesitis, and dactylitis) was reported in 51 patients (63%). Data regarding axial disease (sacroiliitis and ankylosing spondylitis) were only available in 37 patients, 19 of whom reported axial distribution. Peripheral and axial MSK symptoms followed the course of bowel disease in 40.3% and 28.1% of patients respectively, which were not significantly different.

Conclusion: MSK EIMs affect 6.1% of a contemporary cohort of Canadian pIBD patients. This is less than reported in literature, which may be related to physician-reported nature of our data. Their phenotype is variable, with peripheral disease more frequent than axial disease across IBD types.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/phenotype-of-musculoskeletal-manifestations-in-a-canadian-inception-cohort-of-pediatric-patients-with-inflammatory-bowel-disease/