PO:19:283 | Hospitalization profile and complications in patients with adult-onset Still’s disease: results from a retrospective study of 74 cases

Chiara Calabrese¹, Alessandro Tomelleri^1|2, Corrado Campochiaro^1|2, Nicola Farina², Elena Baldissera², Marco Matucci-Cerinic^1|2, Lorenzo Dagna^1|2 | ¹Libera Università Vita-Salute San Raffaele, Milano; ²Unità di Immunologia, Allergologia e malattie rare, IRCCS San Raffaele, Milano, Italy

Background. Adult-onset Still’s disease (AOSD) is a rare systemic inflammatory disorder that may follow a severe course with potentially life-threatening complications. The aim of this study was to describe hospitalization patterns and major complications in a retrospective cohort of patients with AOSD.

Materials and Methods. A retrospective study was conducted on patients with AOSD followed between January 2009 and May 2025 at a single tertiary center. Demographic, clinical, and laboratory data at disease onset were collected, along with information on hospitalizations (number, duration, causes, and timing) and therapies administered during admission. The incidence of macrophage activation syndrome (MAS), its temporal relationship with disease onset, and the treatments employed were also evaluated. Data were analyzed descriptively using medians, interquartile ranges (IQR), and absolute frequencies.

Results. Seventy-four patients were included (median age at onset 35 years, IQR 25–47; 50% female), with a median follow-up of 54 months (IQR 31–147). Forty patients (54%) experienced a single hospitalization, and 20 (27%) had two or more. Forty-six patients (62%) were hospitalized at disease onset, among whom 9 presented with MAS. Of those with MAS, 3 (33%) had a second hospitalization within 3 years. Among patients hospitalized at onset, the median length of stay was 21.2 days (IQR 14.8–27.5), and treatment included glucocorticoids (98%), anakinra (22%), and cyclosporine A (15%). During follow-up, 26 additional hospitalizations were recorded at a median of 29 months after diagnosis (IQR 1.5–88). The main causes of hospitalization were AOSD relapse (n=16, 62%; associated with MAS in 6 cases), infections (n=5, 19%), cardiovascular events (n=3, 12%), and neurological events (n=3, 11.5%). Relapses occurred while patients were receiving systemic corticosteroids at a median prednisone dose of 20 mg (IQR 7.2–37.5); 8 patients were on anakinra and 12 on methotrexate. Management included corticosteroid escalation in all cases, initiation of anakinra in 6 patients, and cyclosporine A in 4. Infectious complications included 2 upper respiratory tract infections, 4 pneumonias, 3 urinary tract infections, 1 E. coli urosepsis, 1 HBV hepatitis, 1 Granulicatella adiacens bacteremia, and 1 varicella-zoster virus reactivation. At the time of infection, patients were receiving a median of 1 mg prednisone (IQR 0–10.5); 2 were on anakinra, 4 on cyclosporine A, 2 on methotrexate, and 1 on canakinumab.

Conclusions. AOSD is frequently associated with hospitalization, particularly at disease onset, with a substantial proportion of patients experiencing multiple admissions. MAS and infections are the most common—and potentially late—complications. Structured monitoring and careful adjustment of immunosuppressive therapy are essential to minimize relapses and reduce complications.