Indeed, the ORM2 expression levels were much greater in the sera and synovial fluids of the RA patients than in those of the OA patients (mean ± SEM: 3.5 ± 0.47 μg/mL vs. 0.26 ± 0.04 μg/mL in the sera and 8.7 ± 1.8 μg/mL vs. 0.12 ± 0.04 μg/mL in the synovial fluids) (Fig. 1b). Here, ORM2 is linked to rheumatoid arthritis.