Sung Soo Ahn, Byung-Woo Yoo, Seung Min Jung, Sang-Won Lee, Yong-Beom Park, Jason Jungsik Song

To evaluate the clinical significance of the 2016 European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR)/Pediatric Rheumatology International Trials Organization (PRINTO) classification criteria for macrophage activation syndrome (MAS) in patients with adult-onset Still disease (AOSD). We performed a retrospective analysis of patients with AOSD with fever who were admitted to Severance Hospital between 2005 and 2016. The patients with AOSD were evaluated for MAS using the 2016 classification criteria for MAS. Clinical features, laboratory findings, and overall survival were analyzed. Logistic regression analysis was used to evaluate the factors associated with in-hospital mortality. Among 64 patients with AOSD, 36 (56.3%) were classified as having MAS. The overall survival rate was significantly lower in patients with MAS than in those without (67% vs 100%, p < 0.001). Multivariate analysis showed that a low erythrocyte sedimentation rate, a low albumin level, an increase in ferritin of over 2 folds, and the development of MAS on admission were significantly associated with mortality in patients with AOSD. The 2016 EULAR/ACR/PRINTO classification criteria for MAS are potentially useful for the identification of patients with AOSD at high risk for a poor outcome. Febrile patients with AOSD should be monitored with the 2016 classification criteria for MAS in the early diagnosis and proper treatment of MAS.