Hydroxychloroquine for the First Thrombosis Prevention in Antiphospholipid Antibody Positive Patients

Inclusion Criteria: * Persistent(at least 12 weeks apart)aPL-positivity within 12 months prior to the screening defined as: * aCL IgG/M (\>40U,medium-to-high titer,and/or greater than the 99th percentile)and/or * aβ2GPI IgG/M(\>40U, medium-to-high titer, and/or greater than the 99th percentile)and/or * Positive LA test based on the International Society of Thrombosis \& Haematosis Recommendations Selected Exclusion Criteria: * History of thrombosis (arterial, venous, and/or biopsy proven microthrombosis * History of Transient Ischemic Attack Confirmed by a Neurologist * SLE Diagnosis based on the ACR Classification Criteria \> 4/11 * Other Systemic Autoimmune Diseases diagnosed based on ACR Classification Criteria * Current Hydroxychloroquine or another antimalarial treatment (-3 months) * Current warfarin treatment (-3 months) * Current heparin therapy( -3 months) * Current pregnancy * History of Hydroxychloroquine eye toxicity * History of Hydroxychloroquine allergy * Known glucose-6-phosphate dehydrogenase deficiency