Autoinflammatory diseases (AIDs) are a group of rare disorders caused by dysregulation of the innate immune system, characterized by recurrent fever, systemic inflammation, and involvement of specific organs. Diagnosis relies on a combination of clinical features, laboratory tests, genetic findings, and response to treatment. Still's disease is a representative type of AID, marked by high spiking fevers, polyarthritis, evanescent rash, and markedly elevated inflammatory markers. Among its complications, macrophage activation syndrome (MAS) is the most life-threatening, affecting approximately 10-15% of patients. MAS involves uncontrolled immune activation and systemic inflammation, and if left untreated, may result in a mortality rate exceeding 50%. This study aims to develop a standardized clinical dataset and diagnostic-treatment framework for AIDs based on their disease characteristics. After establishing a data collection template, eligible patients aged 18-75 years with AIDs will be enrolled. Clinical data will be collected to build a prospective follow-up cohort, focusing particularly on adult-onset Still's disease (AOSD), to explore the clinical features and pathogenesis of AIDs.