**2. Precipitating factors in CAPS**

Infections

Postpartum or recent fetal loss

Minor surgical procedures or surgery

Other: malignancy, medication, anticoagulation withdrawal, and SLE exacerbation.

Although the pathogenesis of CAPS continues to be insufficiently understood, antiphospholipid (aPL) antibodies (Ab) belong to the immunoglobulin (Ig) family and are directed against phospholipid-binding plasma proteins such as Beta2 Glycoprotein1 (B2- GP1), prothrombin, annexin V, PS, PC, etc.

As a consequence of initial damage, anionic phospholipids would be exposed on the cell surface B2-GP1. If there are circulating anti-B2-GP1 Ab, they will bind to this complex, inducing cell activation with the release of tissue factor (TF), adhesion molecules, IL-8, C3b, C5a, among others, such as the activation of leukocytes and platelets. This increases their adhesion to the vascular endothelium, promoting microthrombosis and promoting the release of proteases and free radicals. Multiple vascular occlusion triggers necrosis tissue with excessive release of cytokines. A present marker is ferritin, which is elevated in 71% of CAPS patients and according to a recent study could play a role in the pathogenesis of APS and as a follow-up marker in CAPS [6, 7].

Kitchen postulates that vascular occlusion triggers additional thrombosis ("thrombotic storm"), which leads to increased thrombin and decreased fibrinolysis. As her son proposes the theory of "molecular mimic-cry" (molecular imitation), where on one hand the anti-B2-GP1 Ab when bound to the B2-GP1 of *COVID-19 and Catastrophic Antiphospholipid Syndrome DOI: http://dx.doi.org/10.5772/intechopen.99896*

the endothelial cell generate a procoagulant state and on the other hand, certain viruses and bacteria that have an amino acid sequence similar to that of B2-GP1. This therefore favors the synthesis of more Ab. Furthermore, B2-GP1 could activate the immune response through interaction with a membrane receptor TLRs (tolllike) and from this a series of signals are generated, which increase the production of proinflammatory cytokines (TNF, IL-1B, IL-6, IL.8) and FT, PAI-1, PAF, etc. leading to multi-organ failure [8].
