Background/Purpose:

Some studies have suggested that chronic recurrent multifocal osteomyelitis (CRMO) and spondyloarthropathies (SpA) fall on a spectrum of disease, as they have been noted to share overlapping radiographic and clinical features. Most studies examining the link between inflammatory bone lesions and SpA have involved adult patients with SAPHO syndrome, with limited pediatric data. This study was done to test whether gender, HLA-B27 positivity, or age at onset of disease, influence whether and when pediatric CRMO and SpA patients develop overlapping features. Understanding of the clinical factors influencing overlap may have implications for earlier diagnosis, risk stratification, and treatment options.

Methods:

This was a retrospective inception cohort study of SickKids hospital charts. Eligible pediatric patients diagnosed with either CRMO or SpA between January 2000 and December 2016 were collected using the SickKids Rheumatology patient database. Using a secure web application (REDCap), we collected and compared the clinical, laboratory, and radiographic data of 40 randomly sampled patients from each of the CRMO and SpA groups. The MRIs were re-read by a radiologist. A patient was considered to have an overlap diagnosis if they had radiologic and clinical features of both CRMO and SpA.

Results:

7 patients (17.5%) and 8 patients (20.0%) from the CRMO and SpA groups, respectively, developed overlap. The median time to overlap was 36.0 months and 31.5 months, respectively. A survival (time-to-event) analysis, using the Kaplan-Meier approach, was used to show the proportion of patients without overlap features, since time of symptom onset. 28% of the entire sample population was HLA-B27 positive. Multivariable regression models using the Cox Proportional Hazards regression technique showed that the overall likelihood ratio test was not statistically significant (p=0.59), with hazard ratios of 1.11, 0.91, and 1.17 for each of male gender, HLA-27 positivity, and age at symptom onset, respectively.

Conclusion:

Patient gender, HLA-B27 positivity, and age of symptom onset did not appear to increase the risk of developing overlap features of CRMO and SpA in our sample population. Nonetheless, overlap of clinical and radiologic features was found in approximately 20% of our patients. CRMO and SpA may represent two diseases on the same spectrum, though prospective studies with longer follow up are needed. Our study was limited by the small sample size and retrospective design, as it is unknown whether overlap may occur in the time exceeding clinical follow-up. Study of their clinical overlap is important to allow a better understanding of how to recognize and treat these rare diseases.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-retrospective-study-of-clinical-factors-influencing-the-development-of-overlapping-disease-features-in-pediatric-patients-with-chronic-recurrent-multifocal-osteomyelitis-crmo-and-spondyloarthropat/