CRP and Sacroiliac arthritis: In particular, 2(33.3%) UPIA patients were defined as having RA because of the development of >10 joints involvement and both abnormal CRP and ESR (13), 2(33.3%) as having PsA (due to the subsequent development of psoriasis, psoriatic nail dystrophy and dactylitis) (14) and 2(33.3%) as having SpA (due to the subsequent development of sacroiliitis on imaging) (15), respectively.