Inclusion Criteria:  meet 2006 Sapporo classification criteria of APS; diagnosis of primary APS, exclude other etiologies of thrombosis; with three aPL medium-to-high titer positivity, namely lupus anticoagulant, anti cardiolipin antibody, and anti-β2 glycoprotein antibody; with at least one extra-criteria manifestations of APS, including thrombocytopenia, hemolytic anemia, aPL nephropathy, valve heart disease and neurological manifestations.  Exclusion Criteria:  overlap with other connective tissue diseases, such as systemic lupus erythematosus; during pregnancy; can not follow-up.