Adult-onset Still’s disease, sometimes known as AOSD, is a rare type of inflammatory arthritis. As the name suggests, it can only be diagnosed in adults. Its name comes from another condition, Still’s disease, which is also known as systemic juvenile idiopathic arthritis (JIA). Systemic JIA is only diagnosed in children. 32 rows · Jun 29, · Adult-onset Still's disease (AOSD) is an inflammatory condition that affects multiple.