Study Overview: This study looks at Macrophage Activation Syndrome (MAS) in patients with Still's disease. MAS is when certain immune cells, called macrophages, become overactive. Still's disease is a type of arthritis that can happen in kids (systemic Juvenile Idiopathic Arthritis or sJIA) or adults (Adult Onset Still's Disease or AOSD). The study uses past medical records to find out how patients with MAS responded to steroid treatments called glucocorticoids (GC), especially when these treatments didn't work well.

Who Can Join: People aged over 6 months and up to 80 years, diagnosed with Still’s disease and MAS between 2012 and 2022, and who had at least 3 days of GC treatment. If you were diagnosed with a condition called primary Hemophagocytic Lymphohistiocytosis (HLH) or had cancer before MAS, or were part of another clinical trial, you cannot join.

• No new visits or tests: All information comes from existing medical records.
• No direct risk involved: Since it’s a chart review, there’s no treatment or tests involved.
• No compensation: Participants won't receive any payment for this study.