Similarities between pediatric FMF patients with sacroiliitis and pediatric juvenile spondyloarthropathy patients with sacroiliitis: a preliminary study

Objective: Familial Mediterranean fever (FMF) is an autosomal recessive disease characterized by recurrent, self-limited attacks of fever with serositis. Acute recurrent arthritis is the most common form of musculoskeletal involvement in FMF; however, ≤5% of FMF patients can develop chronic arthritis, including sacroiliitis. It is difficult to determine if sacroiliitis is a musculoskeletal finding of FMF or if they are concomitant diseases-FMF and juvenile spondyloarthropathy (JSpA). The present study aimed to compare clinical and laboratory findings in FMF patients with concomitant sacroiliitis and JSpA patients with concomitant sacroiliitis.Materials and Methods: The medical files of patients diagnosed with FMF and JSpA with concomitant sacroiliitis were retrospectively evaluated. All patients had MRI findings consistent with sacroiliitis. Patient demographic data, clinical features, and laboratory findings were compared between the patients with FMF and concomitant sacroiliitis, and those with JSpA and concomitant sacroiliitis.Results: The study included 18 patients with FMF and sacroiliitis, and 38 patients with JSpA and sacroiliitis. The median (range) age at diagnosis of FMF accompanied by sacroiliitis and JSpA accompanied by sacroiliitis was 12.0 years (3.5-18 years) and 13 years (4-18 years), respectively. There weren't any significant differences in HLA-B27 positivity, family history of ankylosing spondylitis, presenting complaints, arthritis, enthesitis, or treatment between the 2 patient groups.Conclusion: The present findings show that pediatric patients with FMF and sacroiliitis, and those with JSpA and sacroiliitis have the same clinical and laboratory findings.