“…To date, AAS has mostly been reported in rheumatoid arthritis (RA) 3,4 , with a prevalence of 12%-33% and even up to 86% in some reports 5,6 . The prevalence is 2%-6.7% and up to 21% in AS 2,7,8,9,10,11,12 , other spondy-loarthropathies 7,13,14 , and rarely, mixed connective tissue disease 15 , systemic lupus erythematosus 16 , and Behçet's disease 17,18 . Although most patients with AAS remain asymptomatic in AS as well as in RA 19 , about 32% show radiologic progression during followup 20 .…”