AAU patients with sacroiliitis had significantly higher disease activity compared to patients without sacroiliitis (ASDAS: 1.46 (0.93–2.05) vs. 0.9 (0.64–1.53) respectively, p = 0.006; CRP: 4.43 (1.76–10.44) vs. 1.22 (0.65–2.92) respectively, p < 0.0001). This evidence concerns the gene CRP and Sacroiliac arthritis.