Abstract
Objective Adult-onset Still's disease (AOSD) is a rare orphan disease, the diagnosis of which remains challenging. This study aimed to identify additional clues for establishing early diagnosis beyond the existing criteria. Methods A retrospective longitudinal cohort study was conducted at two community hospitals in Japan between March 2012 and December 2022. The clinical characteristics and medical histories of patients with AOSD were extracted from the clinical records. The primary outcome was to identify the key manifestations of AOSD for an early diagnosis beyond the existing criteria. Results Twenty-one patients (mean age, 58 years) were included in the study. Fever was the first symptom in 13 out of 21 patients (62%). Six out of 21 patients (29%) presented with a pruritic rash only, while two out of 21 (10%) initially presented with a sore throat. All patients visited more than one medical institution. The median time to reach a correct diagnosis was 41 days (IQR 19-138). Nineteen out of 20 patients (95%) exhibited a pruritic rash, identified as persistent pruritic linear streaks, with a median duration of 21 days (IQR 12-64) before the diagnosis of AOSD as a cutaneous manifestation. Conclusions Persistent pruritic linear streaks were a key feature in the context of an early diagnosis of AOSD, offering an option for reconsidering and revising the existing classification criteria.