Background: Recently, the incidence of late-onset Still’s disease has been increasing, but its clinical and immunologic characteristics are still unclear.

Objectives: Recently, the incidence of old patients with adult Still’s disease has been increasing, but its clinical and immunological characteristics are still unclear.

Methods: We reviewed consecutive patients with adult Still’s disease diagnosed based on Yamaguchi criteria at Keio University Hospital between April 2012 and June 2024. Patients were divided into two groups, young-onset and late-onset, with a cut-off age of the onset of 65 years. We compared clinical characteristics and peripheral blood immunophenotypes between the two groups.

Results: Of the 113 patients with adult Still’s disease, 20 (17.6%) were late-onset. The median age was 40 and 72 years, and the proportion of the female was 71% and 70% in the young-onset and late-onset groups, respectively. At the time of diagnosis, the proportion of patients with sore throat (71% vs 40%, p=0.02), typical rash (69% vs 40%, p=0.02), and splenomegaly (54% vs 21%, p=0.01) was significantly lower in the late-onset group than in the young-onset group, whereas those with serositis (11% vs 70%, p<0.001) and interstitial pneumonia (5% vs 26%, p=0.01) was significantly higher in the late-onset group. Peripheral blood immunophenotyping was performed in 5 in the young-onset group and 4 in the late-onset group. The proportion of T peripheral helper (Tph) cells among all lymphocytes was significantly higher in the late-onset group (0.45% vs. 0.92%, p=0.03). The percentage of Tph cells was positively correlated with age (ρ=0.74, p=0.04), serum IgG (ρ=0.75, p=0.04), and percentage of plasma cells (ρ=0.61, p=0.11), and tended to be inversely correlated with C-reactive protein (ρ=-0.57, p=0.15).

Conclusion: The distribution of affected organs and the features of immune cells in the peripheral blood were different in late-onset patients compared to young-onset patients. Increased Tph cells in late-onset patients may contribute to the differences in the pathophysiology of adult Still’s disease.

REFERENCES: NIL.

Figure 1.

Acknowledgements: NIL.

Disclosure of Interests: Moe Fukuchi: None declared , Satoshi Takanashi: None declared , Kie Tanaka: None declared , Hiroya Tamai: None declared , Yasushi Kondo: None declared , Noriyasu Seki employed by Mitsubishi Tanabe Pharma Corporation, Kenji Chiba employed by Mitsubishi Tanabe Pharma Corporation, Keiko Yoshimoto: None declared , Yuko Kaneko: None declared .

© The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.