Objectives:
The aim of the study was to evaluate the efficacy and long-term safety of tocilizumab treatment in children with systemic-onset juvenile idiopathic arthritis in a single centre.

Material and methods:
The study was based on a retrospective analysis of a cohort of 10 patients with systemic-onset juvenile idiopathic arthritis who were treated with tocilizumab in the period September 2011–July 2017. Their medical records were analysed taking into consideration the effectiveness of tocilizumab treatment and frequency of side effects.

Results:
Before the initiation of treatment, 9/10 patients from the study group complained of fever and had significantly increased values of inflammatory markers, with the median CRP concentration 41.1 mg/l (norm < 5 mg/l) and ESR 37 mm/h (norm < 12 mg/l). The period of the initial 12 weeks of treatment was a quantum leap in the course of the disease: all children were afebrile, and inflammatory markers values decreased by 99.4% in the case of CRP and 91.9% in ESR. All patients fulfilled ACR Pedi 50 criteria, and 3 of them achieved ACR Pedi 70. In the next stages of treatment the response to tocilizumab was sustained, reaching 10 children achieving ACR Pedi 70 and 5 ACR Pedi 90 after one year of therapy. Tocilizumab appeared to be relatively safe in the study group. Although elevation of transaminases and neutropenia were observed in 5/10 patients, they were usually mild and transitional in their course.

Conclusions:
Tocilizumab is both effective and has a relatively good safety profile in children with severe systemic-onset juvenile idiopathic arthritis. It should be considered in the recommendations as a first-line treatment of this disease.