Hydroxychloroquine (HCQ) is an antimalarial drug, also used to treat rheumatic diseases such as SLE. There is experimental evidence to suggest a direct role of hydroxychloroquine on the pathophysiology of APS: it directly reduces the binding of antibodies on the phospholipid bilayers, protects the annexin A5 anticoagulant shield and it reverses platelet adhesion induced by aPL.