Clinical course, complications and treatment outcomes in Still's disease: a 10-year single-centre cohort study

To evaluate the long-term outcomes, clinical phenotypes and factors associated with complications in Still's disease (systemic juvenile idiopathic arthritis) based on data from a 10-year single-centre cohort.

This retrospective observational study included 110 patients with Still's disease/systemic juvenile idiopathic arthritis (sJIA) followed between 2015 and 2025 at a tertiary paediatric rheumatology centre. Demographic, clinical and laboratory parameters were analysed for associations with macrophage activation syndrome (MAS), interstitial lung disease (ILD), disease course and treatment outcomes. Statistical analyses included non-parametric tests, correlation analyses and logistic regression.

MAS occurred in 36.7% of patients, nearly half at disease onset. Serositis at diagnosis was associated with subsequent MAS, while low haemoglobin and erythrocyte sedimentation rate reflected concurrent MAS features. ILD was observed in 8.2% of patients and was strongly associated with MAS and a polycyclic disease course. Older age at onset and the presence of rash were independently associated with a polycyclic course. Early anakinra initiation was more frequent in severe cases but was not independently associated with improved long-term outcomes.

This 10-year cohort demonstrates marked heterogeneity in Still's disease/sJIA. MAS and ILD frequently co-occur and indicate a more aggressive course. Clinical features such as serositis may help identify patients at risk, whereas laboratory abnormalities should be interpreted in the context of active MAS.