Several mechanisms have been proposed for the pathogenesis of catastrophic APS such as molecular mimicry, infections, activation of endothelium microvasculature, and small vessel occlusions resulting in SIRS and release of inflammatory cytokines, products of complement (C3, C5) who in combination with aPL antibodies have led to thrombosis characteristic of CAPS [3]. This evidence concerns the gene C5 and systemic inflammatory response syndrome.