ANALYSIS OF INTERFERON TYPE I SIGNATURE IN JUVENILE DERMATOMYOSITIS

Background: the crucial role of hyperactivation IFN I signaling pathway has been proved in the pathogenesis of dermatomyositis. IFN I genes and chemokines activity vary according to subtype of inflammatory myopathies. IFN type 1 signature could be measured using different genes in the blood, skin and muscle tissue [1]. Objectives: to evaluate IFN-score in children with dermatomyositis and compare with disease activity Methods: 15 patients (5 boys and 10 girls) were enrolled in the study. Clinical and laboratory parameters, disease activity (CMAS-childhood myositis assessment tool, aCAT- abbreviated cutaneous assessment tool) and treatment were assessed. Patients were compared accordingly to IFN-score elevation. IFN I-score was assessed by RT-PCR quantitation of 5 IFN I-regulated transcripts (IFI44L, IFI44, IFIT3, LY6E, MXA1); median relative expression of ≥ 2 was considered as a cut-off. IFN I-score was evaluated in dynamics in 9 patients. Results: median age of patients was 6.2 (3.6; 7.6) years. Skin and muscle involvement were in all patients, arthritis in 5 (33%) patients, calcinosis in 3 (20%), lipodystrophy in 2 (13%) and lung involvement in 5 patients (33%), and 9 patients (60%) had positive myositis-related antibodies. Ten patients (67%) had an active disease, while elevated IFN-signature was detected in 12 (80%) patients. Cumulative IFN I-score and its’ five components were higher in active patients, compare to inactive (13.6 vs 1.4, p=0.006). Patients with increased IFN I-score had lower CMAS score and higher aCAT score compare to patients with normal levels of IFN I-score. IFN-I score correlated with aCAT, arthritis and lung involvement. Conclusion: IFN-I score may be considered as disease activity biomarker in juvenile dermatomyositis with predominantly skin activity process. REFERENCES: [1]Rigolet M, Hou C, Baba Amer Y, Aouizerate J, Periou B, Gherardi RK et al. Distinct interferon signatures stratify inflammatory and dysimmune myopathies. RMD Open. 2019 Feb 26;5(1):e000811. doi: 10.1136/rmdopen-2018-000811. PMID: 30886734; PMCID: PMC6397431. Acknowledgements: This work was supported by the RSF grant № 20-45-01005 Disclosure of Interests: None declared Citation: , volume 81, supplement 1, year 2022, page 993Session: Paediatric rheumatology (POSTERS only)