EULAR proposes new guidance to assess disease activity in adult-onset Still’s disease

EULAR - The European Alliance of Associations for Rheumatology - has identified an unmet clinical need around the assessment of disease activity in people with adult-onset Still's disease. New points to consider aim to address this gap, and provide the basis for developing a reliable and simple tool for clinical practice.

Adult-onset Still's disease (AOSD) is a rare inflammatory disorder. Thanks to a new initiative, AOSD is now considered to be the adult counterpart of systemic juvenile idiopathic arthritis, but in both cases the cause is unknown. People with AOSD typically have fever, arthritis, a skin rash, and systemic involvement across multiple organs. But there can be differing clinical patterns - both in individual people's presentation and across flare and remission. Although there are treatment options for people with AOSD, there is no accepted definition for what constitutes a clinical response to these, making it hard to compare results across different studies, or to set management goals in the clinic.

To address this, EULAR put together a task force of healthcare professionals and patient research partners. Experts were asked to suggest suitable clinical features for measuring disease activity, and the candidates were assessed and voted on over a series of meetings. The aim was to move towards specific criteria for a definition. Having a clear definition of disease activity is important, and may help to identify patients who require more aggressive treatment.

The manuscript - published in the December 2025 issue of EULAR Rheumatology Open - includes three overarching principles and 11 points to consider. The principles emphasise the importance of adopting a definition of disease activity that is valid, reliable, and easily transferable in any clinical setting. The development of specific criteria for assessing disease activity should include a precise definition of the clinical features which could better describe the patient condition.

The points to consider outline the need to include fever as one of the variables of the core set. Other items highlighted are skin rash, arthritis and arthralgia, and systemic involvement. Laboratory findings such as hyperferritinemia, inflammatory markers, and increased white blood cell count can also be useful - both at onset and for identifying relapse and flare - and transaminases are a useful marker of systemic involvement.

A key need alongside a definition of disease activity is an objective definition of remission - the ideal clinical target in many rheumatological diseases. Also still to be developed is a disease-specific patient-reported outcome that can assess the patient perspective.

Establishing a reproducible definition of remission could help us move towards a new therapeutic target that we can use both in trials and in the clinic. "This will definitively initiate the era of treat-to-target in AOSD."

Roberto Giacomelli, corresponding author on the paper and Professor of Rheumatology at the Fondazione Policlinico Campus Bio-Medico in Rome, Italy

The new points to consider should be read in conjunction with the 2024 recommendations on the diagnosis and management of both children and adults with Still's disease.¹ Of note, the recommendations include the absence of disease-related signs together with normal inflammatory markers as a definition for clinically inactive disease - and persistence for 6 months without need for glucocorticoids as a definition for remission. However, these are based on findings in children more than adults, and so it remains to be seen whether there will be complete overlap across the age span. For instance, some characteristics such as splenomegaly and hepatomegaly are more common in adults than children, and adults also have other comorbidities, and these differences could impact the definitions. However, it is also important to note that - since SJIA and AOSD are now considered a unique disease - a joint effort is needed to achieve uniform management.

EULAR hope these new points to consider will provide the basis for a reliable tool that can be easily applied in clinical settings in order to help improve management for people with AOSD.