<s>[INST] <<SYS>> This is a medical question of type : causes <</SYS>> What causes Adult-onset Still's disease ? [/INST] What causes adult-onset Still's disease? The cause of adult-onset Stills disease is unknown. Some hypothesize that the condition results from or is triggered by a virus or other infectious agent. Others believe that it is a hypersensitive or autoimmune disorder. To date, no conclusive evidence has been found to prove or disprove either theory. </s>