Clinical and epidemiological characteristics of juvenile idiopathic arthritis in pediatric residents of the Republic of Sakha (Yakutia), Russia

Due to the ethnic and geographical features, the incidence of rheumatic diseases in the Republic of Sakha (Yakutia), Russia, differs from it in other Russia regions. The purposes of this research were to describe the epidemiological, demographic, clinical and laboratory characteristics of pediatric patients with juvenile idiopathic arthritis (JIA) residing on the territory of the Republic of Sakha (Yakutia), Russia (RSY), to describe the therapeutical options and to evaluate the main outcomes. Materials and methods used: the continuous single-center cohort retrospective study included data from medical records of all patients (225) with diagnosed JIA who had undergone examination and treatment in the cardiorheumatological department of the Pediatric Center with the Sakha (Yakutia) Republican Hospital No. 1 - M.E. Nikolaev National Medicine Center (Yakutsk, Republic of Sakha (Yakutia), Russia) in 2016-2023. Results: the incidence of JIA in the RSY regional pediatric population aged 0 to 17 y/o was increasing noticeably, from 5.3 per 100,000 in 2016 to 15.5 per 100,000 in 2023, i.e. almost tripled (2.9) or by 192.9%. The 2023 RSY JIA prevalence was 84.5 and was higher in children living in rural areas - 102.8 per 100,000 children, than in cities - 73.6 per 100,000 children. By ethnicity, the JIA prevalence was higher in the Yakut children - 110.1 per 100,000, than in children of the Russian nationality - 69.4 per 100,000. Among the Yakut children living in the cities, the JIA prevalence was higher (139.4 per 100,000) than in those living in rural areas (89.8 per 100,000). The JIA prevalence among the Yakut boys and girls was identical whilst girls had predominated amongst the Russian children. The distribution of patients by JIA categories was as follows: juvenile arthritis with systemic onset counted for 3.5%, oligoarthritis - 33.8%, RF-positive polyarthritis - 0.9%, RF-negative polyarthritis - 14.7%, enthesitis-associated arthritis (EAA) - 44%, psoriatic arthritis - 3.1%. The frequency of uveitis was 10.2%, HLA-B27 carriage was 39.6%, seropositivity for ANF was 66.7%. The prevalence of EAA was 4.4 times higher in the Yakut children, and the systemic form was 2.9 times lower than that in Russians (p<0.001). 40.4% of children with JIA received therapy with genetically engineered biological drugs, with remission achieved in this group in 45.4% of cases. Conclusion: JIA in RSY has its own epidemiological, clinical and laboratory features associated with the prevalence of the HLA-B27 amongst the Yakut pediatric population. The Yakut children are more likely to suffer from JIA, the disease prevails among boys, the most common JIA form was EEA whilst uveitis and psoriasis being the rare extra-articular JIA manifestations.