In APS, but not in VTE patients plasma C5b-C9 correlated with clot-bound C5-C9 amounts (r = 0.46, p = 0.031) and plasma HRG was associated with the clot-bound HRG (r = 0.34, p = 0.028), while negative associations were observed between plasma and clot-bound apo A-I (r = −0.64, p = 0.0011) and apo B-100 (r = −0.39, p = 0.048). This evidence concerns the gene C5 and autoimmune polyendocrinopathy.