Spondyloarthropathies are all autoimmune diseases that affect the joints, and they're seronegative, which refers to the fact that rheumatoid factor, which is an autoantibody, is not found in the blood.
脊柱关节病是一类累及关节、且血清学呈阴性的自身免疫病；血清学阴性是指患者血液中未发现类风湿因子这种自身抗体。