[1] The syndrome is caused by antiphospholipid antibodies that target a group of proteins in the body that are associated with phospholipids.

The body contains β2-GPI, a glycoprotein in the blood, which is considered a natural anticoagulant due to its inhibitory effects on certain aspects of platelet synthesis and function.

[3] A thrombotic storm may also occur due to the following precipitating events: alterations in coagulation and fibrinolysis, which induce high mortality rates, and infections amongst pediatric patients where IgM and IgG anti-β2-GPI antibodies induce an endothelial signal, leading to a procoagulant state.

An enzyme-linked immunosorbent assay (ELISA) test is done to detect anticardiolipin antibodies' presence in the blood.

[9] Individuals with CAPS often exhibit a positive test to antilipid antibodies, typically IgG.

Association with another disease such as lupus is called a secondary APS unless it includes the defining criteria for CAPS.