Systemic-Onset Juvenile Arthritis: Epidemiology, Clinical Picture, Differential Diagnosis in Physician’s Practice (Results of a Two-Center Retrospective Cohort Study)

Systemic-onset juvenile arthritis (sJIA) is an acute and severe disease characterized by systemic inflammation, arthritis and extra-articular manifestations. Until now, sJIA is considered to be a diagnosis of “exception” requiring careful differential diagnosis coupled with a number of other diseases. The purpose of this research was to evaluate the demographic features of sJIA, analyze clinical and laboratory data, patients’ compliance with diagnostic criteria according to the International League of Associations for Rheumatology's (ILAR) established criteria, and identify difficulties at the stage of differential diagnosis. Materials and methods used: a multicenter (two-center) retrospective cohort study was conducted among 65 pediatric patients aged 8 months to 17 y/o (27/41.5% girls and 38/58.5% boys) with an established diagnosis of sJIA in 2013-2022 in two clinical centers as follows: University Children’s Clinical Hospital of the N.F. Filatov Clinical Institute of Children’s Health with the I.M. Sechenov First Moscow State Medical University and Morozov Children’s City Clinical Hospital (both located in Moscow, Russia). Anamnesis of the disease, complaints upon admission, examination data upon admission, laboratory test results, including clinical and biochemical blood tests, immunological parameters (IgA, IgM and IgG), myelogram data, abdominal ultrasound, echocardiography, computed tomography of the chest and abdominal organs with intravenous bolus contrast and brain MRI were analyzed. Results: the disease onset occurs in the first 10 years of life (87.7% 73.6%; 94.8%) in most cases with the age of onset in boys (6 3; 9 years) and girls (5 1.6; 8 years) did not differ statistically significantly (p=0.499). Characteristic for sJIA is the early age of onset of the disease, in 31 patients (47.7%) the diagnosis was made before the age of 6 years, from 6 to 10 y/o - in 26 (40.0%), from 11 to 16 y/o - in 8 (12.3%). According to the results of instrumental analysis, pericarditis prevailed among serositis, while a gender predisposition in the development of pericarditis in girls was identified (p=0.036). Conclusion: the difficulty of differential diagnosis lies in the absence of pathognomonic symptoms, biomarkers characteristic of sJIA, and therefore, to make a diagnosis, a number of diseases with similar symptoms should be excluded at first.