Clues for inflammatory diseases in the differential diagnosis of a child with sacroiliitis

BACKGROUND: The purpose of this study was to compare the demographic, clinical and laboratory characteristics of patients with enthesitis-related arthritis (ERA), familial Mediterranean fever (FMF) and inflammatory bowel disease (IBD), which are inflammatory diseases that may develop sacroiliitis. Thus, it was aimed to reveal various findings that may indicate primary disease in patients with sacroiliitis. METHODS: Pediatric patients aged 6-18 years, who were being followed with a diagnosis of ERA (n = 62), FMF (n = 590), and IBD (n = 56) over the period 2013-2021 were included in the study. Sacroiliitis (n = 55) was diagnosed by magnetic resonance imaging of the sacroiliac joint, obtained from clinically suspected patients. RESULTS: Sacroiliitis was detected in 54.8% of ERA patients, 2.3% of FMF patients, and 12.5% of IBD patients. The mean follow-up period was 4.1 ± 2.8 years (10 months-8 years) for the entire study group. The most common MRI finding for sacroiliitis was bone marrow edema. Peripheral joint involvement (73.5%) and HLA B27 positivity (64.7%) was significantly higher in ERA patients, and ERA was diagnosed more frequently in patients presenting with sacroiliitis. Non-steroidal anti-inflammatory drugs (NSAIDs) were the first choice of treatment agent when sacroiliitis developed in all three patient groups. CONCLUSIONS: The clinical and laboratory findings of ERA, FMF and IBD can sometimes be intertwined or can even coexist. Treatment may differ depending on the disease associated with sacroiliitis, although NSAIDs may be used in the first-line treatment of all three diseases. Sacroiliitis patients with HLA B27 positivity and peripheral arthritis may need to be addressed as ERA.